/*
** 2001 September 15
**
** The author disclaims copyright to this source code. In place of
** a legal notice, here is a blessing:
**
** May you do good and not evil.
** May you find forgiveness for yourself and forgive others.
** May you share freely, never taking more than you give.
**
*************************************************************************
** This is the implementation of the page cache subsystem or "pager".
**
** The pager is used to access a database disk file. It implements
** atomic commit and rollback through the use of a journal file that
** is separate from the database file. The pager also implements file
** locking to prevent two processes from writing the same database
** file simultaneously, or one process from reading the database while
** another is writing.
**
** @(#) $Id: pager.c,v 1.586.2.1 2009/05/18 17:11:31 drh Exp $
*/
#ifndef SQLITE_OMIT_DISKIO
#include "sqliteInt.h"
/*
** Macros for troubleshooting. Normally turned off
*/
#if 0
int sqlite3PagerTrace=1; /* True to enable tracing */
#define sqlite3DebugPrintf printf
#define PAGERTRACE(X) if( sqlite3PagerTrace ){ sqlite3DebugPrintf X; }
#else
#define PAGERTRACE(X)
#endif
/*
** The following two macros are used within the PAGERTRACE() macros above
** to print out file-descriptors.
**
** PAGERID() takes a pointer to a Pager struct as its argument. The
** associated file-descriptor is returned. FILEHANDLEID() takes an sqlite3_file
** struct as its argument.
*/
#define PAGERID(p) ((int)(p->fd))
#define FILEHANDLEID(fd) ((int)fd)
/*
** The page cache as a whole is always in one of the following
** states:
**
** PAGER_UNLOCK The page cache is not currently reading or
** writing the database file. There is no
** data held in memory. This is the initial
** state.
**
** PAGER_SHARED The page cache is reading the database.
** Writing is not permitted. There can be
** multiple readers accessing the same database
** file at the same time.
**
** PAGER_RESERVED This process has reserved the database for writing
** but has not yet made any changes. Only one process
** at a time can reserve the database. The original
** database file has not been modified so other
** processes may still be reading the on-disk
** database file.
**
** PAGER_EXCLUSIVE The page cache is writing the database.
** Access is exclusive. No other processes or
** threads can be reading or writing while one
** process is writing.
**
** PAGER_SYNCED The pager moves to this state from PAGER_EXCLUSIVE
** after all dirty pages have been written to the
** database file and the file has been synced to
** disk. All that remains to do is to remove or
** truncate the journal file and the transaction
** will be committed.
**
** The page cache comes up in PAGER_UNLOCK. The first time a
** sqlite3PagerGet() occurs, the state transitions to PAGER_SHARED.
** After all pages have been released using sqlite_page_unref(),
** the state transitions back to PAGER_UNLOCK. The first time
** that sqlite3PagerWrite() is called, the state transitions to
** PAGER_RESERVED. (Note that sqlite3PagerWrite() can only be
** called on an outstanding page which means that the pager must
** be in PAGER_SHARED before it transitions to PAGER_RESERVED.)
** PAGER_RESERVED means that there is an open rollback journal.
** The transition to PAGER_EXCLUSIVE occurs before any changes
** are made to the database file, though writes to the rollback
** journal occurs with just PAGER_RESERVED. After an sqlite3PagerRollback()
** or sqlite3PagerCommitPhaseTwo(), the state can go back to PAGER_SHARED,
** or it can stay at PAGER_EXCLUSIVE if we are in exclusive access mode.
*/
#define PAGER_UNLOCK 0
#define PAGER_SHARED 1 /* same as SHARED_LOCK */
#define PAGER_RESERVED 2 /* same as RESERVED_LOCK */
#define PAGER_EXCLUSIVE 4 /* same as EXCLUSIVE_LOCK */
#define PAGER_SYNCED 5
/*
** A macro used for invoking the codec if there is one
*/
#ifdef SQLITE_HAS_CODEC
# define CODEC1(P,D,N,X) if( P->xCodec!=0 ){ P->xCodec(P->pCodecArg,D,N,X); }
# define CODEC2(P,D,N,X) ((char*)(P->xCodec!=0?P->xCodec(P->pCodecArg,D,N,X):D))
#else
# define CODEC1(P,D,N,X) /* NO-OP */
# define CODEC2(P,D,N,X) ((char*)D)
#endif
/*
** The maximum allowed sector size. 16MB. If the xSectorsize() method
** returns a value larger than this, then MAX_SECTOR_SIZE is used instead.
** This could conceivably cause corruption following a power failure on
** such a system. This is currently an undocumented limit.
*/
#define MAX_SECTOR_SIZE 0x0100000
/*
** An instance of the following structure is allocated for each active
** savepoint and statement transaction in the system. All such structures
** are stored in the Pager.aSavepoint[] array, which is allocated and
** resized using sqlite3Realloc().
**
** When a savepoint is created, the PagerSavepoint.iHdrOffset field is
** set to 0. If a journal-header is written into the main journal while
** the savepoint is active, then iHdrOffset is set to the byte offset
** immediately following the last journal record written into the main
** journal before the journal-header. This is required during savepoint
** rollback (see pagerPlaybackSavepoint()).
*/
typedef struct PagerSavepoint PagerSavepoint;
struct PagerSavepoint {
i64 iOffset; /* Starting offset in main journal */
i64 iHdrOffset; /* See above */
Bitvec *pInSavepoint; /* Set of pages in this savepoint */
Pgno nOrig; /* Original number of pages in file */
Pgno iSubRec; /* Index of first record in sub-journal */
};
/*
** A open page cache is an instance of the following structure.
**
** errCode
**
** Pager.errCode may be set to SQLITE_IOERR, SQLITE_CORRUPT, or
** or SQLITE_FULL. Once one of the first three errors occurs, it persists
** and is returned as the result of every major pager API call. The
** SQLITE_FULL return code is slightly different. It persists only until the
** next successful rollback is performed on the pager cache. Also,
** SQLITE_FULL does not affect the sqlite3PagerGet() and sqlite3PagerLookup()
** APIs, they may still be used successfully.
**
** dbSizeValid, dbSize, dbOrigSize, dbFileSize
**
** Managing the size of the database file in pages is a little complicated.
** The variable Pager.dbSize contains the number of pages that the database
** image currently contains. As the database image grows or shrinks this
** variable is updated. The variable Pager.dbFileSize contains the number
** of pages in the database file. This may be different from Pager.dbSize
** if some pages have been appended to the database image but not yet written
** out from the cache to the actual file on disk. Or if the image has been
** truncated by an incremental-vacuum operation. The Pager.dbOrigSize variable
** contains the number of pages in the database image when the current
** transaction was opened. The contents of all three of these variables is
** only guaranteed to be correct if the boolean Pager.dbSizeValid is true.
**
** TODO: Under what conditions is dbSizeValid set? Cleared?
**
** changeCountDone
**
** This boolean variable is used to make sure that the change-counter
** (the 4-byte header field at byte offset 24 of the database file) is
** not updated more often than necessary.
**
** It is set to true when the change-counter field is updated, which
** can only happen if an exclusive lock is held on the database file.
** It is cleared (set to false) whenever an exclusive lock is
** relinquished on the database file. Each time a transaction is committed,
** The changeCountDone flag is inspected. If it is true, the work of
** updating the change-counter is omitted for the current transaction.
**
** This mechanism means that when running in exclusive mode, a connection
** need only update the change-counter once, for the first transaction
** committed.
**
** dbModified
**
** The dbModified flag is set whenever a database page is dirtied.
** It is cleared at the end of each transaction.
**
** It is used when committing or otherwise ending a transaction. If
** the dbModified flag is clear then less work has to be done.
**
** journalStarted
**
** This flag is set whenever the the main journal is synced.
**
** The point of this flag is that it must be set after the
** first journal header in a journal file has been synced to disk.
** After this has happened, new pages appended to the database
** do not need the PGHDR_NEED_SYNC flag set, as they do not need
** to wait for a journal sync before they can be written out to
** the database file (see function pager_write()).
**
** setMaster
**
** This variable is used to ensure that the master journal file name
** (if any) is only written into the journal file once.
**
** When committing a transaction, the master journal file name (if any)
** may be written into the journal file while the pager is still in
** PAGER_RESERVED state (see CommitPhaseOne() for the action). It
** then attempts to upgrade to an exclusive lock. If this attempt
** fails, then SQLITE_BUSY may be returned to the user and the user
** may attempt to commit the transaction again later (calling
** CommitPhaseOne() again). This flag is used to ensure that the
** master journal name is only written to the journal file the first
** time CommitPhaseOne() is called.
**
** doNotSync
**
** This variable is set and cleared by sqlite3PagerWrite().
**
** needSync
**
** TODO: It might be easier to set this variable in writeJournalHdr()
** and writeMasterJournal() only. Change its meaning to "unsynced data
** has been written to the journal".
**
** subjInMemory
**
** This is a boolean variable. If true, then any required sub-journal
** is opened as an in-memory journal file. If false, then in-memory
** sub-journals are only used for in-memory pager files.
*/
struct Pager {
sqlite3_vfs *pVfs; /* OS functions to use for IO */
u8 exclusiveMode; /* Boolean. True if locking_mode==EXCLUSIVE */
u8 journalMode; /* On of the PAGER_JOURNALMODE_* values */
u8 useJournal; /* Use a rollback journal on this file */
u8 noReadlock; /* Do not bother to obtain readlocks */
u8 noSync; /* Do not sync the journal if true */
u8 fullSync; /* Do extra syncs of the journal for robustness */
u8 sync_flags; /* One of SYNC_NORMAL or SYNC_FULL */
u8 tempFile; /* zFilename is a temporary file */
u8 readOnly; /* True for a read-only database */
u8 memDb; /* True to inhibit all file I/O */
/* The following block contains those class members that are dynamically
** modified during normal operations. The other variables in this structure
** are either constant throughout the lifetime of the pager, or else
** used to store configuration parameters that affect the way the pager
** operates.
**
** The 'state' variable is described in more detail along with the
** descriptions of the values it may take - PAGER_UNLOCK etc. Many of the
** other variables in this block are described in the comment directly
** above this class definition.
*/
u8 state; /* PAGER_UNLOCK, _SHARED, _RESERVED, etc. */
u8 dbModified; /* True if there are any changes to the Db */
u8 needSync; /* True if an fsync() is needed on the journal */
u8 journalStarted; /* True if header of journal is synced */
u8 changeCountDone; /* Set after incrementing the change-counter */
u8 setMaster; /* True if a m-j name has been written to jrnl */
u8 doNotSync; /* Boolean. While true, do not spill the cache */
u8 dbSizeValid; /* Set when dbSize is correct */
u8 subjInMemory; /* True to use in-memory sub-journals */
Pgno dbSize; /* Number of pages in the database */
Pgno dbOrigSize; /* dbSize before the current transaction */
Pgno dbFileSize; /* Number of pages in the database file */
int errCode; /* One of several kinds of errors */
int nRec; /* Pages journalled since last j-header written */
u32 cksumInit; /* Quasi-random value added to every checksum */
u32 nSubRec; /* Number of records written to sub-journal */
Bitvec *pInJournal; /* One bit for each page in the database file */
sqlite3_file *fd; /* File descriptor for database */
sqlite3_file *jfd; /* File descriptor for main journal */
sqlite3_file *sjfd; /* File descriptor for sub-journal */
i64 journalOff; /* Current write offset in the journal file */
i64 journalHdr; /* Byte offset to previous journal header */
PagerSavepoint *aSavepoint; /* Array of active savepoints */
int nSavepoint; /* Number of elements in aSavepoint[] */
char dbFileVers[16]; /* Changes whenever database file changes */
u32 sectorSize; /* Assumed sector size during rollback */
int nExtra; /* Add this many bytes to each in-memory page */
u32 vfsFlags; /* Flags for sqlite3_vfs.xOpen() */
int pageSize; /* Number of bytes in a page */
Pgno mxPgno; /* Maximum allowed size of the database */
char *zFilename; /* Name of the database file */
char *zJournal; /* Name of the journal file */
int (*xBusyHandler)(void*); /* Function to call when busy */
void *pBusyHandlerArg; /* Context argument for xBusyHandler */
#ifdef SQLITE_TEST
int nHit, nMiss; /* Cache hits and missing */
int nRead, nWrite; /* Database pages read/written */
#endif
void (*xReiniter)(DbPage*); /* Call this routine when reloading pages */
#ifdef SQLITE_HAS_CODEC
void *(*xCodec)(void*,void*,Pgno,int); /* Routine for en/decoding data */
void *pCodecArg; /* First argument to xCodec() */
#endif
char *pTmpSpace; /* Pager.pageSize bytes of space for tmp use */
i64 journalSizeLimit; /* Size limit for persistent journal files */
PCache *pPCache; /* Pointer to page cache object */
sqlite3_backup *pBackup; /* Pointer to list of ongoing backup processes */
};
/*
** The following global variables hold counters used for
** testing purposes only. These variables do not exist in
** a non-testing build. These variables are not thread-safe.
*/
#ifdef SQLITE_TEST
int sqlite3_pager_readdb_count = 0; /* Number of full pages read from DB */
int sqlite3_pager_writedb_count = 0; /* Number of full pages written to DB */
int sqlite3_pager_writej_count = 0; /* Number of pages written to journal */
# define PAGER_INCR(v) v++
#else
# define PAGER_INCR(v)
#endif
/*
** Journal files begin with the following magic string. The data
** was obtained from /dev/random. It is used only as a sanity check.
**
** Since version 2.8.0, the journal format contains additional sanity
** checking information. If the power fails while the journal is being
** written, semi-random garbage data might appear in the journal
** file after power is restored. If an attempt is then made
** to roll the journal back, the database could be corrupted. The additional
** sanity checking data is an attempt to discover the garbage in the
** journal and ignore it.
**
** The sanity checking information for the new journal format consists
** of a 32-bit checksum on each page of data. The checksum covers both
** the page number and the pPager->pageSize bytes of data for the page.
** This cksum is initialized to a 32-bit random value that appears in the
** journal file right after the header. The random initializer is important,
** because garbage data that appears at the end of a journal is likely
** data that was once in other files that have now been deleted. If the
** garbage data came from an obsolete journal file, the checksums might
** be correct. But by initializing the checksum to random value which
** is different for every journal, we minimize that risk.
*/
static const unsigned char aJournalMagic[] = {
0xd9, 0xd5, 0x05, 0xf9, 0x20, 0xa1, 0x63, 0xd7,
};
/*
** The size of the of each page record in the journal is given by
** the following macro.
*/
#define JOURNAL_PG_SZ(pPager) ((pPager->pageSize) + 8)
/*
** The journal header size for this pager. This is usually the same
** size as a single disk sector. See also setSectorSize().
*/
#define JOURNAL_HDR_SZ(pPager) (pPager->sectorSize)
/*
** The macro MEMDB is true if we are dealing with an in-memory database.
** We do this as a macro so that if the SQLITE_OMIT_MEMORYDB macro is set,
** the value of MEMDB will be a constant and the compiler will optimize
** out code that would never execute.
*/
#ifdef SQLITE_OMIT_MEMORYDB
# define MEMDB 0
#else
# define MEMDB pPager->memDb
#endif
/*
** The maximum legal page number is (2^31 - 1).
*/
#define PAGER_MAX_PGNO 2147483647
#ifndef NDEBUG
/*
** Usage:
**
** assert( assert_pager_state(pPager) );
*/
static int assert_pager_state(Pager *pPager){
/* A temp-file is always in PAGER_EXCLUSIVE or PAGER_SYNCED state. */
assert( pPager->tempFile==0 || pPager->state>=PAGER_EXCLUSIVE );
/* The changeCountDone flag is always set for temp-files */
assert( pPager->tempFile==0 || pPager->changeCountDone );
return 1;
}
#endif
/*
** Return true if it is necessary to write page *pPg into the sub-journal.
** A page needs to be written into the sub-journal if there exists one
** or more open savepoints for which:
**
** * The page-number is less than or equal to PagerSavepoint.nOrig, and
** * The bit corresponding to the page-number is not set in
** PagerSavepoint.pInSavepoint.
*/
static int subjRequiresPage(PgHdr *pPg){
Pgno pgno = pPg->pgno;
Pager *pPager = pPg->pPager;
int i;
for(i=0; i<pPager->nSavepoint; i++){
PagerSavepoint *p = &pPager->aSavepoint[i];
if( p->nOrig>=pgno && 0==sqlite3BitvecTest(p->pInSavepoint, pgno) ){
return 1;
}
}
return 0;
}
/*
** Return true if the page is already in the journal file.
*/
static int pageInJournal(PgHdr *pPg){
return sqlite3BitvecTest(pPg->pPager->pInJournal, pPg->pgno);
}
/*
** Read a 32-bit integer from the given file descriptor. Store the integer
** that is read in *pRes. Return SQLITE_OK if everything worked, or an
** error code is something goes wrong.
**
** All values are stored on disk as big-endian.
*/
static int read32bits(sqlite3_file *fd, i64 offset, u32 *pRes){
unsigned char ac[4];
int rc = sqlite3OsRead(fd, ac, sizeof(ac), offset);
if( rc==SQLITE_OK ){
*pRes = sqlite3Get4byte(ac);
}
return rc;
}
/*
** Write a 32-bit integer into a string buffer in big-endian byte order.
*/
#define put32bits(A,B) sqlite3Put4byte((u8*)A,B)
/*
** Write a 32-bit integer into the given file descriptor. Return SQLITE_OK
** on success or an error code is something goes wrong.
*/
static int write32bits(sqlite3_file *fd, i64 offset, u32 val){
char ac[4];
put32bits(ac, val);
return sqlite3OsWrite(fd, ac, 4, offset);
}
/*
** The argument to this macro is a file descriptor (type sqlite3_file*).
** Return 0 if it is not open, or non-zero (but not 1) if it is.
**
** This is so that expressions can be written as:
**
** if( isOpen(pPager->jfd) ){ ...
**
** instead of
**
** if( pPager->jfd->pMethods ){ ...
*/
#define isOpen(pFd) ((pFd)->pMethods)
/*
** If file pFd is open, call sqlite3OsUnlock() on it.
*/
static int osUnlock(sqlite3_file *pFd, int eLock){
if( !isOpen(pFd) ){
return SQLITE_OK;
}
return sqlite3OsUnlock(pFd, eLock);
}
/*
** This function determines whether or not the atomic-write optimization
** can be used with this pager. The optimization can be used if:
**
** (a) the value returned by OsDeviceCharacteristics() indicates that
** a database page may be written atomically, and
** (b) the value returned by OsSectorSize() is less than or equal
** to the page size.
**
** The optimization is also always enabled for temporary files. It is
** an error to call this function if pPager is opened on an in-memory
** database.
**
** If the optimization cannot be used, 0 is returned. If it can be used,
** then the value returned is the size of the journal file when it
** contains rollback data for exactly one page.
*/
#ifdef SQLITE_ENABLE_ATOMIC_WRITE
static int jrnlBufferSize(Pager *pPager){
assert( !MEMDB );
if( !pPager->tempFile ){
int dc; /* Device characteristics */
int nSector; /* Sector size */
int szPage; /* Page size */
assert( isOpen(pPager->fd) );
dc = sqlite3OsDeviceCharacteristics(pPager->fd);
nSector = pPager->sectorSize;
szPage = pPager->pageSize;
assert(SQLITE_IOCAP_ATOMIC512==(512>>8));
assert(SQLITE_IOCAP_ATOMIC64K==(65536>>8));
if( 0==(dc&(SQLITE_IOCAP_ATOMIC|(szPage>>8)) || nSector>szPage) ){
return 0;
}
}
return JOURNAL_HDR_SZ(pPager) + JOURNAL_PG_SZ(pPager);
}
#endif
/*
** If SQLITE_CHECK_PAGES is defined then we do some sanity checking
** on the cache using a hash function. This is used for testing
** and debugging only.
*/
#ifdef SQLITE_CHECK_PAGES
/*
** Return a 32-bit hash of the page data for pPage.
*/
static u32 pager_datahash(int nByte, unsigned char *pData){
u32 hash = 0;
int i;
for(i=0; i<nByte; i++){
hash = (hash*1039) + pData[i];
}
return hash;
}
static u32 pager_pagehash(PgHdr *pPage){
return pager_datahash(pPage->pPager->pageSize, (unsigned char *)pPage->pData);
}
static void pager_set_pagehash(PgHdr *pPage){
pPage->pageHash = pager_pagehash(pPage);
}
/*
** The CHECK_PAGE macro takes a PgHdr* as an argument. If SQLITE_CHECK_PAGES
** is defined, and NDEBUG is not defined, an assert() statement checks
** that the page is either dirty or still matches the calculated page-hash.
*/
#define CHECK_PAGE(x) checkPage(x)
static void checkPage(PgHdr *pPg){
Pager *pPager = pPg->pPager;
assert( !pPg->pageHash || pPager->errCode
|| (pPg->flags&PGHDR_DIRTY) || pPg->pageHash==pager_pagehash(pPg) );
}
#else
#define pager_datahash(X,Y) 0
#define pager_pagehash(X) 0
#define CHECK_PAGE(x)
#endif /* SQLITE_CHECK_PAGES */
/*
** When this is called the journal file for pager pPager must be open.
** This function attempts to read a master journal file name from the
** end of the file and, if successful, copies it into memory supplied
** by the caller. See comments above writeMasterJournal() for the format
** used to store a master journal file name at the end of a journal file.
**
** zMaster must point to a buffer of at least nMaster bytes allocated by
** the caller. This should be sqlite3_vfs.mxPathname+1 (to ensure there is
** enough space to write the master journal name). If the master journal
** name in the journal is longer than nMaster bytes (including a
** nul-terminator), then this is handled as if no master journal name
** were present in the journal.
**
** If a master journal file name is present at the end of the journal
** file, then it is copied into the buffer pointed to by zMaster. A
** nul-terminator byte is appended to the buffer following the master
** journal file name.
**
** If it is determined that no master journal file name is present
** zMaster[0] is set to 0 and SQLITE_OK returned.
**
** If an error occurs while reading from the journal file, an SQLite
** error code is returned.
*/
static int readMasterJournal(sqlite3_file *pJrnl, char *zMaster, u32 nMaster){
int rc; /* Return code */
u32 len; /* Length in bytes of master journal name */
i64 szJ; /* Total size in bytes of journal file pJrnl */
u32 cksum; /* MJ checksum value read from journal */
u32 u; /* Unsigned loop counter */
unsigned char aMagic[8]; /* A buffer to hold the magic header */
zMaster[0] = '\0';
if( SQLITE_OK!=(rc = sqlite3OsFileSize(pJrnl, &szJ))
|| szJ<16
|| SQLITE_OK!=(rc = read32bits(pJrnl, szJ-16, &len))
|| len>=nMaster
|| SQLITE_OK!=(rc = read32bits(pJrnl, szJ-12, &cksum))
|| SQLITE_OK!=(rc = sqlite3OsRead(pJrnl, aMagic, 8, szJ-8))
|| memcmp(aMagic, aJournalMagic, 8)
|| SQLITE_OK!=(rc = sqlite3OsRead(pJrnl, zMaster, len, szJ-16-len))
){
return rc;
}
/* See if the checksum matches the master journal name */
for(u=0; u<len; u++){
cksum -= zMaster[u];
}
if( cksum ){
/* If the checksum doesn't add up, then one or more of the disk sectors
** containing the master journal filename is corrupted. This means
** definitely roll back, so just return SQLITE_OK and report a (nul)
** master-journal filename.
*/
len = 0;
}
zMaster[len] = '\0';
return SQLITE_OK;
}
/*
** Return the offset of the sector boundary at or immediately
** following the value in pPager->journalOff, assuming a sector
** size of pPager->sectorSize bytes.
**
** i.e for a sector size of 512:
**
** Pager.journalOff Return value
** ---------------------------------------
** 0 0
** 512 512
** 100 512
** 2000 2048
**
*/
static i64 journalHdrOffset(Pager *pPager){
i64 offset = 0;
i64 c = pPager->journalOff;
if( c ){
offset = ((c-1)/JOURNAL_HDR_SZ(pPager) + 1) * JOURNAL_HDR_SZ(pPager);
}
assert( offset%JOURNAL_HDR_SZ(pPager)==0 );
assert( offset>=c );
assert( (offset-c)<JOURNAL_HDR_SZ(pPager) );
return offset;
}
/*
** The journal file must be open when this function is called.
**
** This function is a no-op if the journal file has not been written to
** within the current transaction (i.e. if Pager.journalOff==0).
**
** If doTruncate is non-zero or the Pager.journalSizeLimit variable is
** set to 0, then truncate the journal file to zero bytes in size. Otherwise,
** zero the 28-byte header at the start of the journal file. In either case,
** if the pager is not in no-sync mode, sync the journal file immediately
** after writing or truncating it.
**
** If Pager.journalSizeLimit is set to a positive, non-zero value, and
** following the truncation or zeroing described above the size of the
** journal file in bytes is larger than this value, then truncate the
** journal file to Pager.journalSizeLimit bytes. The journal file does
** not need to be synced following this operation.
**
** If an IO error occurs, abandon processing and return the IO error code.
** Otherwise, return SQLITE_OK.
*/
static int zeroJournalHdr(Pager *pPager, int doTruncate){
int rc = SQLITE_OK; /* Return code */
assert( isOpen(pPager->jfd) );
if( pPager->journalOff ){
const i64 iLimit = pPager->journalSizeLimit; /* Local cache of jsl */
IOTRACE(("JZEROHDR %p\n", pPager))
if( doTruncate || iLimit==0 ){
rc = sqlite3OsTruncate(pPager->jfd, 0);
}else{
static const char zeroHdr[28] = {0};
rc = sqlite3OsWrite(pPager->jfd, zeroHdr, sizeof(zeroHdr), 0);
}
if( rc==SQLITE_OK && !pPager->noSync ){
rc = sqlite3OsSync(pPager->jfd, SQLITE_SYNC_DATAONLY|pPager->sync_flags);
}
/* At this point the transaction is committed but the write lock
** is still held on the file. If there is a size limit configured for
** the persistent journal and the journal file currently consumes more
** space than that limit allows for, truncate it now. There is no need
** to sync the file following this operation.
*/
if( rc==SQLITE_OK && iLimit>0 ){
i64 sz;
rc = sqlite3OsFileSize(pPager->jfd, &sz);
if( rc==SQLITE_OK && sz>iLimit ){
rc = sqlite3OsTruncate(pPager->jfd, iLimit);
}
}
}
return rc;
}
/*
** The journal file must be open when this routine is called. A journal
** header (JOURNAL_HDR_SZ bytes) is written into the journal file at the
** current location.
**
** The format for the journal header is as follows:
** - 8 bytes: Magic identifying journal format.
** - 4 bytes: Number of records in journal, or -1 no-sync mode is on.
** - 4 bytes: Random number used for page hash.
** - 4 bytes: Initial database page count.
** - 4 bytes: Sector size used by the process that wrote this journal.
** - 4 bytes: Database page size.
**
** Followed by (JOURNAL_HDR_SZ - 28) bytes of unused space.
*/
static int writeJournalHdr(Pager *pPager){
int rc = SQLITE_OK; /* Return code */
char *zHeader = pPager->pTmpSpace; /* Temporary space used to build header */
u32 nHeader = pPager->pageSize; /* Size of buffer pointed to by zHeader */
u32 nWrite; /* Bytes of header sector written */
int ii; /* Loop counter */
assert( isOpen(pPager->jfd) ); /* Journal file must be open. */
if( nHeader>JOURNAL_HDR_SZ(pPager) ){
nHeader = JOURNAL_HDR_SZ(pPager);
}
/* If there are active savepoints and any of them were created
** since the most recent journal header was written, update the
** PagerSavepoint.iHdrOffset fields now.
*/
for(ii=0; ii<pPager->nSavepoint; ii++){
if( pPager->aSavepoint[ii].iHdrOffset==0 ){
pPager->aSavepoint[ii].iHdrOffset = pPager->journalOff;
}
}
pPager->journalHdr = pPager->journalOff = journalHdrOffset(pPager);
memcpy(zHeader, aJournalMagic, sizeof(aJournalMagic));
/*
** Write the nRec Field - the number of page records that follow this
** journal header. Normally, zero is written to this value at this time.
** After the records are added to the journal (and the journal synced,
** if in full-sync mode), the zero is overwritten with the true number
** of records (see syncJournal()).
**
** A faster alternative is to write 0xFFFFFFFF to the nRec field. When
** reading the journal this value tells SQLite to assume that the
** rest of the journal file contains valid page records. This assumption
** is dangerous, as if a failure occurred whilst writing to the journal
** file it may contain some garbage data. There are two scenarios
** where this risk can be ignored:
**
** * When the pager is in no-sync mode. Corruption can follow a
** power failure in this case anyway.
**
** * When the SQLITE_IOCAP_SAFE_APPEND flag is set. This guarantees
** that garbage data is never appended to the journal file.
*/
assert( isOpen(pPager->fd) || pPager->noSync );
if( (pPager->noSync) || (pPager->journalMode==PAGER_JOURNALMODE_MEMORY)
|| (sqlite3OsDeviceCharacteristics(pPager->fd)&SQLITE_IOCAP_SAFE_APPEND)
){
put32bits(&zHeader[sizeof(aJournalMagic)], 0xffffffff);
}else{
put32bits(&zHeader[sizeof(aJournalMagic)], 0);
}
/* The random check-hash initialiser */
sqlite3_randomness(sizeof(pPager->cksumInit), &pPager->cksumInit);
put32bits(&zHeader[sizeof(aJournalMagic)+4], pPager->cksumInit);
/* The initial database size */
put32bits(&zHeader[sizeof(aJournalMagic)+8], pPager->dbOrigSize);
/* The assumed sector size for this process */
put32bits(&zHeader[sizeof(aJournalMagic)+12], pPager->sectorSize);
/* The page size */
put32bits(&zHeader[sizeof(aJournalMagic)+16], pPager->pageSize);
/* Initializing the tail of the buffer is not necessary. Everything
** works find if the following memset() is omitted. But initializing
** the memory prevents valgrind from complaining, so we are willing to
** take the performance hit.
*/
memset(&zHeader[sizeof(aJournalMagic)+20], 0,
nHeader-(sizeof(aJournalMagic)+20));
/* In theory, it is only necessary to write the 28 bytes that the
** journal header consumes to the journal file here. Then increment the
** Pager.journalOff variable by JOURNAL_HDR_SZ so that the next
** record is written to the following sector (leaving a gap in the file
** that will be implicitly filled in by the OS).
**
** However it has been discovered that on some systems this pattern can
** be significantly slower than contiguously writing data to the file,
** even if that means explicitly writing data to the block of
** (JOURNAL_HDR_SZ - 28) bytes that will not be used. So that is what
** is done.
**
** The loop is required here in case the sector-size is larger than the
** database page size. Since the zHeader buffer is only Pager.pageSize
** bytes in size, more than one call to sqlite3OsWrite() may be required
** to populate the entire journal header sector.
*/
for(nWrite=0; rc==SQLITE_OK&&nWrite<JOURNAL_HDR_SZ(pPager); nWrite+=nHeader){
IOTRACE(("JHDR %p %lld %d\n", pPager, pPager->journalHdr, nHeader))
rc = sqlite3OsWrite(pPager->jfd, zHeader, nHeader, pPager->journalOff);
pPager->journalOff += nHeader;
}
return rc;
}
/*
** The journal file must be open when this is called. A journal header file
** (JOURNAL_HDR_SZ bytes) is read from the current location in the journal
** file. The current location in the journal file is given by
** pPager->journalOff. See comments above function writeJournalHdr() for
** a description of the journal header format.
**
** If the header is read successfully, *pNRec is set to the number of
** page records following this header and *pDbSize is set to the size of the
** database before the transaction began, in pages. Also, pPager->cksumInit
** is set to the value read from the journal header. SQLITE_OK is returned
** in this case.
**
** If the journal header file appears to be corrupted, SQLITE_DONE is
** returned and *pNRec and *PDbSize are undefined. If JOURNAL_HDR_SZ bytes
** cannot be read from the journal file an error code is returned.
*/
static int readJournalHdr(
Pager *pPager, /* Pager object */
i64 journalSize, /* Size of the open journal file in bytes */
u32 *pNRec, /* OUT: Value read from the nRec field */
u32 *pDbSize /* OUT: Value of original database size field */
){
int rc; /* Return code */
unsigned char aMagic[8]; /* A buffer to hold the magic header */
i64 iHdrOff; /* Offset of journal header being read */
assert( isOpen(pPager->jfd) ); /* Journal file must be open. */
/* Advance Pager.journalOff to the start of the next sector. If the
** journal file is too small for there to be a header stored at this
** point, return SQLITE_DONE.
*/
pPager->journalOff = journalHdrOffset(pPager);
if( pPager->journalOff+JOURNAL_HDR_SZ(pPager) > journalSize ){
return SQLITE_DONE;
}
iHdrOff = pPager->journalOff;
/* Read in the first 8 bytes of the journal header. If they do not match
** the magic string found at the start of each journal header, return
** SQLITE_DONE. If an IO error occurs, return an error code. Otherwise,
** proceed.
*/
rc = sqlite3OsRead(pPager->jfd, aMagic, sizeof(aMagic), iHdrOff);
if( rc ){
return rc;
}
if( memcmp(aMagic, aJournalMagic, sizeof(aMagic))!=0 ){
return SQLITE_DONE;
}
/* Read the first three 32-bit fields of the journal header: The nRec
** field, the checksum-initializer and the database size at the start
** of the transaction. Return an error code if anything goes wrong.
*/
if( SQLITE_OK!=(rc = read32bits(pPager->jfd, iHdrOff+8, pNRec))
|| SQLITE_OK!=(rc = read32bits(pPager->jfd, iHdrOff+12, &pPager->cksumInit))
|| SQLITE_OK!=(rc = read32bits(pPager->jfd, iHdrOff+16, pDbSize))
){
return rc;
}
if( pPager->journalOff==0 ){
u32 iPageSize; /* Page-size field of journal header */
u32 iSectorSize; /* Sector-size field of journal header */
u16 iPageSize16; /* Copy of iPageSize in 16-bit variable */
/* Read the page-size and sector-size journal header fields. */
if( SQLITE_OK!=(rc = read32bits(pPager->jfd, iHdrOff+20, &iSectorSize))
|| SQLITE_OK!=(rc = read32bits(pPager->jfd, iHdrOff+24, &iPageSize))
){
return rc;
}
/* Check that the values read from the page-size and sector-size fields
** are within range. To be 'in range', both values need to be a power
** of two greater than or equal to 512, and not greater than their
** respective compile time maximum limits.
*/
if( iPageSize<512 || iSectorSize<512
|| iPageSize>SQLITE_MAX_PAGE_SIZE || iSectorSize>MAX_SECTOR_SIZE
|| ((iPageSize-1)&iPageSize)!=0 || ((iSectorSize-1)&iSectorSize)!=0
){
/* If the either the page-size or sector-size in the journal-header is
** invalid, then the process that wrote the journal-header must have
** crashed before the header was synced. In this case stop reading
** the journal file here.
*/
return SQLITE_DONE;
}
/* Update the page-size to match the value read from the journal.
** Use a testcase() macro to make sure that malloc failure within
** PagerSetPagesize() is tested.
*/
iPageSize16 = (u16)iPageSize;
rc = sqlite3PagerSetPagesize(pPager, &iPageSize16);
testcase( rc!=SQLITE_OK );
assert( rc!=SQLITE_OK || iPageSize16==(u16)iPageSize );
/* Update the assumed sector-size to match the value used by
** the process that created this journal. If this journal was
** created by a process other than this one, then this routine
** is being called from within pager_playback(). The local value
** of Pager.sectorSize is restored at the end of that routine.
*/
pPager->sectorSize = iSectorSize;
}
pPager->journalOff += JOURNAL_HDR_SZ(pPager);
return rc;
}
/*
** Write the supplied master journal name into the journal file for pager
** pPager at the current location. The master journal name must be the last
** thing written to a journal file. If the pager is in full-sync mode, the
** journal file descriptor is advanced to the next sector boundary before
** anything is written. The format is:
**
** + 4 bytes: PAGER_MJ_PGNO.
** + N bytes: Master journal filename in utf-8.
** + 4 bytes: N (length of master journal name in bytes, no nul-terminator).
** + 4 bytes: Master journal name checksum.
** + 8 bytes: aJournalMagic[].
**
** The master journal page checksum is the sum of the bytes in the master
** journal name, where each byte is interpreted as a signed 8-bit integer.
**
** If zMaster is a NULL pointer (occurs for a single database transaction),
** this call is a no-op.
*/
static int writeMasterJournal(Pager *pPager, const char *zMaster){
int rc; /* Return code */
int nMaster; /* Length of string zMaster */
i64 iHdrOff; /* Offset of header in journal file */
i64 jrnlSize; /* Size of journal file on disk */
u32 cksum = 0; /* Checksum of string zMaster */
if( !zMaster || pPager->setMaster
|| pPager->journalMode==PAGER_JOURNALMODE_MEMORY
|| pPager->journalMode==PAGER_JOURNALMODE_OFF
){
return SQLITE_OK;
}
pPager->setMaster = 1;
assert( isOpen(pPager->jfd) );
/* Calculate the length in bytes and the checksum of zMaster */
for(nMaster=0; zMaster[nMaster]; nMaster++){
cksum += zMaster[nMaster];
}
/* If in full-sync mode, advance to the next disk sector before writing
** the master journal name. This is in case the previous page written to
** the journal has already been synced.
*/
if( pPager->fullSync ){
pPager->journalOff = journalHdrOffset(pPager);
}
iHdrOff = pPager->journalOff;
/* Write the master journal data to the end of the journal file. If
** an error occurs, return the error code to the caller.
*/
if( (0 != (rc = write32bits(pPager->jfd, iHdrOff, PAGER_MJ_PGNO(pPager))))
|| (0 != (rc = sqlite3OsWrite(pPager->jfd, zMaster, nMaster, iHdrOff+4)))
|| (0 != (rc = write32bits(pPager->jfd, iHdrOff+4+nMaster, nMaster)))
|| (0 != (rc = write32bits(pPager->jfd, iHdrOff+4+nMaster+4, cksum)))
|| (0 != (rc = sqlite3OsWrite(pPager->jfd, aJournalMagic, 8, iHdrOff+4+nMaster+8)))
){
return rc;
}
pPager->journalOff += (nMaster+20);
pPager->needSync = !pPager->noSync;
/* If the pager is in peristent-journal mode, then the physical
** journal-file may extend past the end of the master-journal name
** and 8 bytes of magic data just written to the file. This is
** dangerous because the code to rollback a hot-journal file
** will not be able to find the master-journal name to determine
** whether or not the journal is hot.
**
** Easiest thing to do in this scenario is to truncate the journal
** file to the required size.
*/
if( SQLITE_OK==(rc = sqlite3OsFileSize(pPager->jfd, &jrnlSize))
&& jrnlSize>pPager->journalOff
){
rc = sqlite3OsTruncate(pPager->jfd, pPager->journalOff);
}
return rc;
}
/*
** Find a page in the hash table given its page number. Return
** a pointer to the page or NULL if the requested page is not
** already in memory.
*/
static PgHdr *pager_lookup(Pager *pPager, Pgno pgno){
PgHdr *p; /* Return value */
/* It is not possible for a call to PcacheFetch() with createFlag==0 to
** fail, since no attempt to allocate dynamic memory will be made.
*/
(void)sqlite3PcacheFetch(pPager->pPCache, pgno, 0, &p);
return p;
}
/*
** Unless the pager is in error-state, discard all in-memory pages. If
** the pager is in error-state, then this call is a no-op.
**
** TODO: Why can we not reset the pager while in error state?
*/
static void pager_reset(Pager *pPager){
if( SQLITE_OK==pPager->errCode ){
sqlite3BackupRestart(pPager->pBackup);
sqlite3PcacheClear(pPager->pPCache);
pPager->dbSizeValid = 0;
}
}
/*
** Free all structures in the Pager.aSavepoint[] array and set both
** Pager.aSavepoint and Pager.nSavepoint to zero. Close the sub-journal
** if it is open and the pager is not in exclusive mode.
*/
static void releaseAllSavepoints(Pager *pPager){
int ii; /* Iterator for looping through Pager.aSavepoint */
for(ii=0; ii<pPager->nSavepoint; ii++){
sqlite3BitvecDestroy(pPager->aSavepoint[ii].pInSavepoint);
}
if( !pPager->exclusiveMode || sqlite3IsMemJournal(pPager->sjfd) ){
sqlite3OsClose(pPager->sjfd);
}
sqlite3_free(pPager->aSavepoint);
pPager->aSavepoint = 0;
pPager->nSavepoint = 0;
pPager->nSubRec = 0;
}
/*
** Set the bit number pgno in the PagerSavepoint.pInSavepoint
** bitvecs of all open savepoints. Return SQLITE_OK if successful
** or SQLITE_NOMEM if a malloc failure occurs.
*/
static int addToSavepointBitvecs(Pager *pPager, Pgno pgno){
int ii; /* Loop counter */
int rc = SQLITE_OK; /* Result code */
for(ii=0; ii<pPager->nSavepoint; ii++){
PagerSavepoint *p = &pPager->aSavepoint[ii];
if( pgno<=p->nOrig ){
rc |= sqlite3BitvecSet(p->pInSavepoint, pgno);
testcase( rc==SQLITE_NOMEM );
assert( rc==SQLITE_OK || rc==SQLITE_NOMEM );
}
}
return rc;
}
/*
** Unlock the database file. This function is a no-op if the pager
** is in exclusive mode.
**
** If the pager is currently in error state, discard the contents of
** the cache and reset the Pager structure internal state. If there is
** an open journal-file, then the next time a shared-lock is obtained
** on the pager file (by this or any other process), it will be
** treated as a hot-journal and rolled back.
*/
static void pager_unlock(Pager *pPager){
if( !pPager->exclusiveMode ){
int rc; /* Return code */
/* Always close the journal file when dropping the database lock.
** Otherwise, another connection with journal_mode=delete might
** delete the file out from under us.
*/
sqlite3OsClose(pPager->jfd);
sqlite3BitvecDestroy(pPager->pInJournal);
pPager->pInJournal = 0;
releaseAllSavepoints(pPager);
/* If the file is unlocked, somebody else might change it. The
** values stored in Pager.dbSize etc. might become invalid if
** this happens. TODO: Really, this doesn't need to be cleared
** until the change-counter check fails in pagerSharedLock().
*/
pPager->dbSizeValid = 0;
rc = osUnlock(pPager->fd, NO_LOCK);
if( rc ){
pPager->errCode = rc;
}
IOTRACE(("UNLOCK %p\n", pPager))
/* If Pager.errCode is set, the contents of the pager cache cannot be
** trusted. Now that the pager file is unlocked, the contents of the
** cache can be discarded and the error code safely cleared.
*/
if( pPager->errCode ){
if( rc==SQLITE_OK ){
pPager->errCode = SQLITE_OK;
}
pager_reset(pPager);
}
pPager->changeCountDone = 0;
pPager->state = PAGER_UNLOCK;
}
}
/*
** This function should be called when an IOERR, CORRUPT or FULL error
** may have occurred. The first argument is a pointer to the pager
** structure, the second the error-code about to be returned by a pager
** API function. The value returned is a copy of the second argument
** to this function.
**
** If the second argument is SQLITE_IOERR, SQLITE_CORRUPT, or SQLITE_FULL
** the error becomes persistent. Until the persisten error is cleared,
** subsequent API calls on this Pager will immediately return the same
** error code.
**
** A persistent error indicates that the contents of the pager-cache
** cannot be trusted. This state can be cleared by completely discarding
** the contents of the pager-cache. If a transaction was active when
** the persistent error occurred, then the rollback journal may need
** to be replayed to restore the contents of the database file (as if
** it were a hot-journal).
*/
static int pager_error(Pager *pPager, int rc){
int rc2 = rc & 0xff;
assert(
pPager->errCode==SQLITE_FULL ||
pPager->errCode==SQLITE_OK ||
(pPager->errCode & 0xff)==SQLITE_IOERR
);
if(
rc2==SQLITE_FULL ||
rc2==SQLITE_IOERR ||
rc2==SQLITE_CORRUPT
){
pPager->errCode = rc;
if( pPager->state==PAGER_UNLOCK
&& sqlite3PcacheRefCount(pPager->pPCache)==0
){
/* If the pager is already unlocked, call pager_unlock() now to
** clear the error state and ensure that the pager-cache is
** completely empty.
*/
pager_unlock(pPager);
}
}
return rc;
}
/*
** Execute a rollback if a transaction is active and unlock the
** database file.
**
** If the pager has already entered the error state, do not attempt
** the rollback at this time. Instead, pager_unlock() is called. The
** call to pager_unlock() will discard all in-memory pages, unlock
** the database file and clear the error state. If this means that
** there is a hot-journal left in the file-system, the next connection
** to obtain a shared lock on the pager (which may be this one) will
** roll it back.
**
** If the pager has not already entered the error state, but an IO or
** malloc error occurs during a rollback, then this will itself cause
** the pager to enter the error state. Which will be cleared by the
** call to pager_unlock(), as described above.
*/
static void pagerUnlockAndRollback(Pager *pPager){
if( pPager->errCode==SQLITE_OK && pPager->state>=PAGER_RESERVED ){
sqlite3BeginBenignMalloc();
sqlite3PagerRollback(pPager);
sqlite3EndBenignMalloc();
}
pager_unlock(pPager);
}
/*
** This routine ends a transaction. A transaction is usually ended by
** either a COMMIT or a ROLLBACK operation. This routine may be called
** after rollback of a hot-journal, or if an error occurs while opening
** the journal file or writing the very first journal-header of a
** database transaction.
**
** If the pager is in PAGER_SHARED or PAGER_UNLOCK state when this
** routine is called, it is a no-op (returns SQLITE_OK).
**
** Otherwise, any active savepoints are released.
**
** If the journal file is open, then it is "finalized". Once a journal
** file has been finalized it is not possible to use it to roll back a
** transaction. Nor will it be considered to be a hot-journal by this
** or any other database connection. Exactly how a journal is finalized
** depends on whether or not the pager is running in exclusive mode and
** the current journal-mode (Pager.journalMode value), as follows:
**
** journalMode==MEMORY
** Journal file descriptor is simply closed. This destroys an
** in-memory journal.
**
** journalMode==TRUNCATE
** Journal file is truncated to zero bytes in size.
**
** journalMode==PERSIST
** The first 28 bytes of the journal file are zeroed. This invalidates
** the first journal header in the file, and hence the entire journal
** file. An invalid journal file cannot be rolled back.
**
** journalMode==DELETE
** The journal file is closed and deleted using sqlite3OsDelete().
**
** If the pager is running in exclusive mode, this method of finalizing
** the journal file is never used. Instead, if the journalMode is
** DELETE and the pager is in exclusive mode, the method described under
** journalMode==PERSIST is used instead.
**
** After the journal is finalized, if running in non-exclusive mode, the
** pager moves to PAGER_SHARED state (and downgrades the lock on the
** database file accordingly).
**
** If the pager is running in exclusive mode and is in PAGER_SYNCED state,
** it moves to PAGER_EXCLUSIVE. No locks are downgraded when running in
** exclusive mode.
**
** SQLITE_OK is returned if no error occurs. If an error occurs during
** any of the IO operations to finalize the journal file or unlock the
** database then the IO error code is returned to the user. If the
** operation to finalize the journal file fails, then the code still
** tries to unlock the database file if not in exclusive mode. If the
** unlock operation fails as well, then the first error code related
** to the first error encountered (the journal finalization one) is
** returned.
*/
static int pager_end_transaction(Pager *pPager, int hasMaster){
int rc = SQLITE_OK; /* Error code from journal finalization operation */
int rc2 = SQLITE_OK; /* Error code from db file unlock operation */
if( pPager->state<PAGER_RESERVED ){
return SQLITE_OK;
}
releaseAllSavepoints(pPager);
assert( isOpen(pPager->jfd) || pPager->pInJournal==0 );
if( isOpen(pPager->jfd) ){
/* TODO: There's a problem here if a journal-file was opened in MEMORY
** mode and then the journal-mode is changed to TRUNCATE or PERSIST
** during the transaction. This code should be changed to assume
** that the journal mode has not changed since the transaction was
** started. And the sqlite3PagerJournalMode() function should be
** changed to make sure that this is the case too.
*/
/* Finalize the journal file. */
if( pPager->journalMode==PAGER_JOURNALMODE_MEMORY ){
int isMemoryJournal = sqlite3IsMemJournal(pPager->jfd);
sqlite3OsClose(pPager->jfd);
if( !isMemoryJournal ){
rc = sqlite3OsDelete(pPager->pVfs, pPager->zJournal, 0);
}
}else if( pPager->journalMode==PAGER_JOURNALMODE_TRUNCATE ){
if( pPager->journalOff==0 ){
rc = SQLITE_OK;
}else{
rc = sqlite3OsTruncate(pPager->jfd, 0);
}
pPager->journalOff = 0;
pPager->journalStarted = 0;
}else if( pPager->exclusiveMode
|| pPager->journalMode==PAGER_JOURNALMODE_PERSIST
){
rc = zeroJournalHdr(pPager, hasMaster);
pager_error(pPager, rc);
pPager->journalOff = 0;
pPager->journalStarted = 0;
}else{
assert( pPager->journalMode==PAGER_JOURNALMODE_DELETE || rc );
sqlite3OsClose(pPager->jfd);
if( rc==SQLITE_OK && !pPager->tempFile ){
rc = sqlite3OsDelete(pPager->pVfs, pPager->zJournal, 0);
}
}
#ifdef SQLITE_CHECK_PAGES
sqlite3PcacheIterateDirty(pPager->pPCache, pager_set_pagehash);
#endif
sqlite3PcacheCleanAll(pPager->pPCache);
sqlite3BitvecDestroy(pPager->pInJournal);
pPager->pInJournal = 0;
pPager->nRec = 0;
}
if( !pPager->exclusiveMode ){
rc2 = osUnlock(pPager->fd, SHARED_LOCK);
pPager->state = PAGER_SHARED;
pPager->changeCountDone = 0;
}else if( pPager->state==PAGER_SYNCED ){
pPager->state = PAGER_EXCLUSIVE;
}
pPager->setMaster = 0;
pPager->needSync = 0;
pPager->dbModified = 0;
/* TODO: Is this optimal? Why is the db size invalidated here
** when the database file is not unlocked? */
pPager->dbOrigSize = 0;
sqlite3PcacheTruncate(pPager->pPCache, pPager->dbSize);
if( !MEMDB ){
pPager->dbSizeValid = 0;
}
return (rc==SQLITE_OK?rc2:rc);
}
/*
** Parameter aData must point to a buffer of pPager->pageSize bytes
** of data. Compute and return a checksum based ont the contents of the
** page of data and the current value of pPager->cksumInit.
**
** This is not a real checksum. It is really just the sum of the
** random initial value (pPager->cksumInit) and every 200th byte
** of the page data, starting with byte offset (pPager->pageSize%200).
** Each byte is interpreted as an 8-bit unsigned integer.
**
** Changing the formula used to compute this checksum results in an
** incompatible journal file format.
**
** If journal corruption occurs due to a power failure, the most likely
** scenario is that one end or the other of the record will be changed.
** It is much less likely that the two ends of the journal record will be
** correct and the middle be corrupt. Thus, this "checksum" scheme,
** though fast and simple, catches the mostly likely kind of corruption.
*/
static u32 pager_cksum(Pager *pPager, const u8 *aData){
u32 cksum = pPager->cksumInit; /* Checksum value to return */
int i = pPager->pageSize-200; /* Loop counter */
while( i>0 ){
cksum += aData[i];
i -= 200;
}
return cksum;
}
/*
** Read a single page from either the journal file (if isMainJrnl==1) or
** from the sub-journal (if isMainJrnl==0) and playback that page.
** The page begins at offset *pOffset into the file. The *pOffset
** value is increased to the start of the next page in the journal.
**
** The isMainJrnl flag is true if this is the main rollback journal and
** false for the statement journal. The main rollback journal uses
** checksums - the statement journal does not.
**
** If the page number of the page record read from the (sub-)journal file
** is greater than the current value of Pager.dbSize, then playback is
** skipped and SQLITE_OK is returned.
**
** If pDone is not NULL, then it is a record of pages that have already
** been played back. If the page at *pOffset has already been played back
** (if the corresponding pDone bit is set) then skip the playback.
** Make sure the pDone bit corresponding to the *pOffset page is set
** prior to returning.
**
** If the page record is successfully read from the (sub-)journal file
** and played back, then SQLITE_OK is returned. If an IO error occurs
** while reading the record from the (sub-)journal file or while writing
** to the database file, then the IO error code is returned. If data
** is successfully read from the (sub-)journal file but appears to be
** corrupted, SQLITE_DONE is returned. Data is considered corrupted in
** two circumstances:
**
** * If the record page-number is illegal (0 or PAGER_MJ_PGNO), or
** * If the record is being rolled back from the main journal file
** and the checksum field does not match the record content.
**
** Neither of these two scenarios are possible during a savepoint rollback.
**
** If this is a savepoint rollback, then memory may have to be dynamically
** allocated by this function. If this is the case and an allocation fails,
** SQLITE_NOMEM is returned.
*/
static int pager_playback_one_page(
Pager *pPager, /* The pager being played back */
int isMainJrnl, /* 1 -> main journal. 0 -> sub-journal. */
int isUnsync, /* True if reading from unsynced main journal */
i64 *pOffset, /* Offset of record to playback */
int isSavepnt, /* True for a savepoint rollback */
Bitvec *pDone /* Bitvec of pages already played back */
){
int rc;
PgHdr *pPg; /* An existing page in the cache */
Pgno pgno; /* The page number of a page in journal */
u32 cksum; /* Checksum used for sanity checking */
u8 *aData; /* Temporary storage for the page */
sqlite3_file *jfd; /* The file descriptor for the journal file */
assert( (isMainJrnl&~1)==0 ); /* isMainJrnl is 0 or 1 */
assert( (isSavepnt&~1)==0 ); /* isSavepnt is 0 or 1 */
assert( isMainJrnl || pDone ); /* pDone always used on sub-journals */
assert( isSavepnt || pDone==0 ); /* pDone never used on non-savepoint */
aData = (u8*)pPager->pTmpSpace;
assert( aData ); /* Temp storage must have already been allocated */
/* Read the page number and page data from the journal or sub-journal
** file. Return an error code to the caller if an IO error occurs.
*/
jfd = isMainJrnl ? pPager->jfd : pPager->sjfd;
rc = read32bits(jfd, *pOffset, &pgno);
if( rc!=SQLITE_OK ) return rc;
rc = sqlite3OsRead(jfd, aData, pPager->pageSize, (*pOffset)+4);
if( rc!=SQLITE_OK ) return rc;
*pOffset += pPager->pageSize + 4 + isMainJrnl*4;
/* Sanity checking on the page. This is more important that I originally
** thought. If a power failure occurs while the journal is being written,
** it could cause invalid data to be written into the journal. We need to
** detect this invalid data (with high probability) and ignore it.
*/
if( pgno==0 || pgno==PAGER_MJ_PGNO(pPager) ){
assert( !isSavepnt );
return SQLITE_DONE;
}
if( pgno>(Pgno)pPager->dbSize || sqlite3BitvecTest(pDone, pgno) ){
return SQLITE_OK;
}
if( isMainJrnl ){
rc = read32bits(jfd, (*pOffset)-4, &cksum);
if( rc ) return rc;
if( !isSavepnt && pager_cksum(pPager, aData)!=cksum ){
return SQLITE_DONE;
}
}
if( pDone && (rc = sqlite3BitvecSet(pDone, pgno))!=SQLITE_OK ){
return rc;
}
assert( pPager->state==PAGER_RESERVED || pPager->state>=PAGER_EXCLUSIVE );
/* If the pager is in RESERVED state, then there must be a copy of this
** page in the pager cache. In this case just update the pager cache,
** not the database file. The page is left marked dirty in this case.
**
** An exception to the above rule: If the database is in no-sync mode
** and a page is moved during an incremental vacuum then the page may
** not be in the pager cache. Later: if a malloc() or IO error occurs
** during a Movepage() call, then the page may not be in the cache
** either. So the condition described in the above paragraph is not
** assert()able.
**
** If in EXCLUSIVE state, then we update the pager cache if it exists
** and the main file. The page is then marked not dirty.
**
** Ticket #1171: The statement journal might contain page content that is
** different from the page content at the start of the transaction.
** This occurs when a page is changed prior to the start of a statement
** then changed again within the statement. When rolling back such a
** statement we must not write to the original database unless we know
** for certain that original page contents are synced into the main rollback
** journal. Otherwise, a power loss might leave modified data in the
** database file without an entry in the rollback journal that can
** restore the database to its original form. Two conditions must be
** met before writing to the database files. (1) the database must be
** locked. (2) we know that the original page content is fully synced
** in the main journal either because the page is not in cache or else
** the page is marked as needSync==0.
**
** 2008-04-14: When attempting to vacuum a corrupt database file, it
** is possible to fail a statement on a database that does not yet exist.
** Do not attempt to write if database file has never been opened.
*/
pPg = pager_lookup(pPager, pgno);
assert( pPg || !MEMDB );
PAGERTRACE(("PLAYBACK %d page %d hash(%08x) %s\n",
PAGERID(pPager), pgno, pager_datahash(pPager->pageSize, aData),
(isMainJrnl?"main-journal":"sub-journal")
));
if( (pPager->state>=PAGER_EXCLUSIVE)
&& (pPg==0 || 0==(pPg->flags&PGHDR_NEED_SYNC))
&& isOpen(pPager->fd)
&& !isUnsync
){
i64 ofst = (pgno-1)*(i64)pPager->pageSize;
rc = sqlite3OsWrite(pPager->fd, aData, pPager->pageSize, ofst);
if( pgno>pPager->dbFileSize ){
pPager->dbFileSize = pgno;
}
sqlite3BackupUpdate(pPager->pBackup, pgno, aData);
}else if( !isMainJrnl && pPg==0 ){
/* If this is a rollback of a savepoint and data was not written to
** the database and the page is not in-memory, there is a potential
** problem. When the page is next fetched by the b-tree layer, it
** will be read from the database file, which may or may not be
** current.
**
** There are a couple of different ways this can happen. All are quite
** obscure. When running in synchronous mode, this can only happen
** if the page is on the free-list at the start of the transaction, then
** populated, then moved using sqlite3PagerMovepage().
**
** The solution is to add an in-memory page to the cache containing
** the data just read from the sub-journal. Mark the page as dirty
** and if the pager requires a journal-sync, then mark the page as
** requiring a journal-sync before it is written.
*/
assert( isSavepnt );
if( (rc = sqlite3PagerAcquire(pPager, pgno, &pPg, 1))!=SQLITE_OK ){
return rc;
}
pPg->flags &= ~PGHDR_NEED_READ;
sqlite3PcacheMakeDirty(pPg);
}
if( pPg ){
/* No page should ever be explicitly rolled back that is in use, except
** for page 1 which is held in use in order to keep the lock on the
** database active. However such a page may be rolled back as a result
** of an internal error resulting in an automatic call to
** sqlite3PagerRollback().
*/
void *pData;
pData = pPg->pData;
memcpy(pData, aData, pPager->pageSize);
if( pPager->xReiniter ){
pPager->xReiniter(pPg);
}
if( isMainJrnl && (!isSavepnt || *pOffset<=pPager->journalHdr) ){
/* If the contents of this page were just restored from the main
** journal file, then its content must be as they were when the
** transaction was first opened. In this case we can mark the page
** as clean, since there will be no need to write it out to the.
**
** There is one exception to this rule. If the page is being rolled
** back as part of a savepoint (or statement) rollback from an
** unsynced portion of the main journal file, then it is not safe
** to mark the page as clean. This is because marking the page as
** clean will clear the PGHDR_NEED_SYNC flag. Since the page is
** already in the journal file (recorded in Pager.pInJournal) and
** the PGHDR_NEED_SYNC flag is cleared, if the page is written to
** again within this transaction, it will be marked as dirty but
** the PGHDR_NEED_SYNC flag will not be set. It could then potentially
** be written out into the database file before its journal file
** segment is synced. If a crash occurs during or following this,
** database corruption may ensue.
*/
sqlite3PcacheMakeClean(pPg);
}
#ifdef SQLITE_CHECK_PAGES
pPg->pageHash = pager_pagehash(pPg);
#endif
/* If this was page 1, then restore the value of Pager.dbFileVers.
** Do this before any decoding. */
if( pgno==1 ){
memcpy(&pPager->dbFileVers, &((u8*)pData)[24],sizeof(pPager->dbFileVers));
}
/* Decode the page just read from disk */
CODEC1(pPager, pData, pPg->pgno, 3);
sqlite3PcacheRelease(pPg);
}
return rc;
}
#if !defined(NDEBUG) || defined(SQLITE_COVERAGE_TEST)
/*
** This routine looks ahead into the main journal file and determines
** whether or not the next record (the record that begins at file
** offset pPager->journalOff) is a well-formed page record consisting
** of a valid page number, pPage->pageSize bytes of content, followed
** by a valid checksum.
**
** The pager never needs to know this in order to do its job. This
** routine is only used from with assert() and testcase() macros.
*/
static int pagerNextJournalPageIsValid(Pager *pPager){
Pgno pgno; /* The page number of the page */
u32 cksum; /* The page checksum */
int rc; /* Return code from read operations */
sqlite3_file *fd; /* The file descriptor from which we are reading */
u8 *aData; /* Content of the page */
/* Read the page number header */
fd = pPager->jfd;
rc = read32bits(fd, pPager->journalOff, &pgno);
if( rc!=SQLITE_OK ){ return 0; } /*NO_TEST*/
if( pgno==0 || pgno==PAGER_MJ_PGNO(pPager) ){ return 0; } /*NO_TEST*/
if( pgno>(Pgno)pPager->dbSize ){ return 0; } /*NO_TEST*/
/* Read the checksum */
rc = read32bits(fd, pPager->journalOff+pPager->pageSize+4, &cksum);
if( rc!=SQLITE_OK ){ return 0; } /*NO_TEST*/
/* Read the data and verify the checksum */
aData = (u8*)pPager->pTmpSpace;
rc = sqlite3OsRead(fd, aData, pPager->pageSize, pPager->journalOff+4);
if( rc!=SQLITE_OK ){ return 0; } /*NO_TEST*/
if( pager_cksum(pPager, aData)!=cksum ){ return 0; } /*NO_TEST*/
/* Reach this point only if the page is valid */
return 1;
}
#endif /* !defined(NDEBUG) || defined(SQLITE_COVERAGE_TEST) */
/*
** Parameter zMaster is the name of a master journal file. A single journal
** file that referred to the master journal file has just been rolled back.
** This routine checks if it is possible to delete the master journal file,
** and does so if it is.
**
** Argument zMaster may point to Pager.pTmpSpace. So that buffer is not
** available for use within this function.
**
** When a master journal file is created, it is populated with the names
** of all of its child journals, one after another, formatted as utf-8
** encoded text. The end of each child journal file is marked with a
** nul-terminator byte (0x00). i.e. the entire contents of a master journal
** file for a transaction involving two databases might be:
**
** "/home/bill/a.db-journal\x00/home/bill/b.db-journal\x00"
**
** A master journal file may only be deleted once all of its child
** journals have been rolled back.
**
** This function reads the contents of the master-journal file into
** memory and loops through each of the child journal names. For
** each child journal, it checks if:
**
** * if the child journal exists, and if so
** * if the child journal contains a reference to master journal
** file zMaster
**
** If a child journal can be found that matches both of the criteria
** above, this function returns without doing anything. Otherwise, if
** no such child journal can be found, file zMaster is deleted from
** the file-system using sqlite3OsDelete().
**
** If an IO error within this function, an error code is returned. This
** function allocates memory by calling sqlite3Malloc(). If an allocation
** fails, SQLITE_NOMEM is returned. Otherwise, if no IO or malloc errors
** occur, SQLITE_OK is returned.
**
** TODO: This function allocates a single block of memory to load
** the entire contents of the master journal file. This could be
** a couple of kilobytes or so - potentially larger than the page
** size.
*/
static int pager_delmaster(Pager *pPager, const char *zMaster){
sqlite3_vfs *pVfs = pPager->pVfs;
int rc; /* Return code */
sqlite3_file *pMaster; /* Malloc'd master-journal file descriptor */
sqlite3_file *pJournal; /* Malloc'd child-journal file descriptor */
char *zMasterJournal = 0; /* Contents of master journal file */
i64 nMasterJournal; /* Size of master journal file */
/* Allocate space for both the pJournal and pMaster file descriptors.
** If successful, open the master journal file for reading.
*/
pMaster = (sqlite3_file *)sqlite3MallocZero(pVfs->szOsFile * 2);
pJournal = (sqlite3_file *)(((u8 *)pMaster) + pVfs->szOsFile);
if( !pMaster ){
rc = SQLITE_NOMEM;
}else{
const int flags = (SQLITE_OPEN_READONLY|SQLITE_OPEN_MASTER_JOURNAL);
rc = sqlite3OsOpen(pVfs, zMaster, pMaster, flags, 0);
}
if( rc!=SQLITE_OK ) goto delmaster_out;
rc = sqlite3OsFileSize(pMaster, &nMasterJournal);
if( rc!=SQLITE_OK ) goto delmaster_out;
if( nMasterJournal>0 ){
char *zJournal;
char *zMasterPtr = 0;
int nMasterPtr = pVfs->mxPathname+1;
/* Load the entire master journal file into space obtained from
** sqlite3_malloc() and pointed to by zMasterJournal.
*/
zMasterJournal = (char *)sqlite3Malloc((int)nMasterJournal + nMasterPtr);
if( !zMasterJournal ){
rc = SQLITE_NOMEM;
goto delmaster_out;
}
zMasterPtr = &zMasterJournal[nMasterJournal];
rc = sqlite3OsRead(pMaster, zMasterJournal, (int)nMasterJournal, 0);
if( rc!=SQLITE_OK ) goto delmaster_out;
zJournal = zMasterJournal;
while( (zJournal-zMasterJournal)<nMasterJournal ){
int exists;
rc = sqlite3OsAccess(pVfs, zJournal, SQLITE_ACCESS_EXISTS, &exists);
if( rc!=SQLITE_OK ){
goto delmaster_out;
}
if( exists ){
/* One of the journals pointed to by the master journal exists.
** Open it and check if it points at the master journal. If
** so, return without deleting the master journal file.
*/
int c;
int flags = (SQLITE_OPEN_READONLY|SQLITE_OPEN_MAIN_JOURNAL);
rc = sqlite3OsOpen(pVfs, zJournal, pJournal, flags, 0);
if( rc!=SQLITE_OK ){
goto delmaster_out;
}
rc = readMasterJournal(pJournal, zMasterPtr, nMasterPtr);
sqlite3OsClose(pJournal);
if( rc!=SQLITE_OK ){
goto delmaster_out;
}
c = zMasterPtr[0]!=0 && strcmp(zMasterPtr, zMaster)==0;
if( c ){
/* We have a match. Do not delete the master journal file. */
goto delmaster_out;
}
}
zJournal += (sqlite3Strlen30(zJournal)+1);
}
}
rc = sqlite3OsDelete(pVfs, zMaster, 0);
delmaster_out:
if( zMasterJournal ){
sqlite3_free(zMasterJournal);
}
if( pMaster ){
sqlite3OsClose(pMaster);
assert( !isOpen(pJournal) );
}
sqlite3_free(pMaster);
return rc;
}
/*
** This function is used to change the actual size of the database
** file in the file-system. This only happens when committing a transaction,
** or rolling back a transaction (including rolling back a hot-journal).
**
** If the main database file is not open, or an exclusive lock is not
** held, this function is a no-op. Otherwise, the size of the file is
** changed to nPage pages (nPage*pPager->pageSize bytes). If the file
** on disk is currently larger than nPage pages, then use the VFS
** xTruncate() method to truncate it.
**
** Or, it might might be the case that the file on disk is smaller than
** nPage pages. Some operating system implementations can get confused if
** you try to truncate a file to some size that is larger than it
** currently is, so detect this case and write a single zero byte to
** the end of the new file instead.
**
** If successful, return SQLITE_OK. If an IO error occurs while modifying
** the database file, return the error code to the caller.
*/
static int pager_truncate(Pager *pPager, Pgno nPage){
int rc = SQLITE_OK;
if( pPager->state>=PAGER_EXCLUSIVE && isOpen(pPager->fd) ){
i64 currentSize, newSize;
/* TODO: Is it safe to use Pager.dbFileSize here? */
rc = sqlite3OsFileSize(pPager->fd, &currentSize);
newSize = pPager->pageSize*(i64)nPage;
if( rc==SQLITE_OK && currentSize!=newSize ){
if( currentSize>newSize ){
rc = sqlite3OsTruncate(pPager->fd, newSize);
}else{
rc = sqlite3OsWrite(pPager->fd, "", 1, newSize-1);
}
if( rc==SQLITE_OK ){
pPager->dbFileSize = nPage;
}
}
}
return rc;
}
/*
** Set the value of the Pager.sectorSize variable for the given
** pager based on the value returned by the xSectorSize method
** of the open database file. The sector size will be used used
** to determine the size and alignment of journal header and
** master journal pointers within created journal files.
**
** For temporary files the effective sector size is always 512 bytes.
**
** Otherwise, for non-temporary files, the effective sector size is
** the value returned by the xSectorSize() method rounded up to 512 if
** it is less than 512, or rounded down to MAX_SECTOR_SIZE if it
** is greater than MAX_SECTOR_SIZE.
*/
static void setSectorSize(Pager *pPager){
assert( isOpen(pPager->fd) || pPager->tempFile );
if( !pPager->tempFile ){
/* Sector size doesn't matter for temporary files. Also, the file
** may not have been opened yet, in which case the OsSectorSize()
** call will segfault.
*/
pPager->sectorSize = sqlite3OsSectorSize(pPager->fd);
}
if( pPager->sectorSize<512 ){
pPager->sectorSize = 512;
}
if( pPager->sectorSize>MAX_SECTOR_SIZE ){
assert( MAX_SECTOR_SIZE>=512 );
pPager->sectorSize = MAX_SECTOR_SIZE;
}
}
/*
** Playback the journal and thus restore the database file to
** the state it was in before we started making changes.
**
** The journal file format is as follows:
**
** (1) 8 byte prefix. A copy of aJournalMagic[].
** (2) 4 byte big-endian integer which is the number of valid page records
** in the journal. If this value is 0xffffffff, then compute the
** number of page records from the journal size.
** (3) 4 byte big-endian integer which is the initial value for the
** sanity checksum.
** (4) 4 byte integer which is the number of pages to truncate the
** database to during a rollback.
** (5) 4 byte big-endian integer which is the sector size. The header
** is this many bytes in size.
** (6) 4 byte big-endian integer which is the page case.
** (7) 4 byte integer which is the number of bytes in the master journal
** name. The value may be zero (indicate that there is no master
** journal.)
** (8) N bytes of the master journal name. The name will be nul-terminated
** and might be shorter than the value read from (5). If the first byte
** of the name is \000 then there is no master journal. The master
** journal name is stored in UTF-8.
** (9) Zero or more pages instances, each as follows:
** + 4 byte page number.
** + pPager->pageSize bytes of data.
** + 4 byte checksum
**
** When we speak of the journal header, we mean the first 8 items above.
** Each entry in the journal is an instance of the 9th item.
**
** Call the value from the second bullet "nRec". nRec is the number of
** valid page entries in the journal. In most cases, you can compute the
** value of nRec from the size of the journal file. But if a power
** failure occurred while the journal was being written, it could be the
** case that the size of the journal file had already been increased but
** the extra entries had not yet made it safely to disk. In such a case,
** the value of nRec computed from the file size would be too large. For
** that reason, we always use the nRec value in the header.
**
** If the nRec value is 0xffffffff it means that nRec should be computed
** from the file size. This value is used when the user selects the
** no-sync option for the journal. A power failure could lead to corruption
** in this case. But for things like temporary table (which will be
** deleted when the power is restored) we don't care.
**
** If the file opened as the journal file is not a well-formed
** journal file then all pages up to the first corrupted page are rolled
** back (or no pages if the journal header is corrupted). The journal file
** is then deleted and SQLITE_OK returned, just as if no corruption had
** been encountered.
**
** If an I/O or malloc() error occurs, the journal-file is not deleted
** and an error code is returned.
**
** The isHot parameter indicates that we are trying to rollback a journal
** that might be a hot journal. Or, it could be that the journal is
** preserved because of JOURNALMODE_PERSIST or JOURNALMODE_TRUNCATE.
** If the journal really is hot, reset the pager cache prior rolling
** back any content. If the journal is merely persistent, no reset is
** needed.
*/
static int pager_playback(Pager *pPager, int isHot){
sqlite3_vfs *pVfs = pPager->pVfs;
i64 szJ; /* Size of the journal file in bytes */
u32 nRec; /* Number of Records in the journal */
u32 u; /* Unsigned loop counter */
Pgno mxPg = 0; /* Size of the original file in pages */
int rc; /* Result code of a subroutine */
int res = 1; /* Value returned by sqlite3OsAccess() */
char *zMaster = 0; /* Name of master journal file if any */
int needPagerReset; /* True to reset page prior to first page rollback */
/* Figure out how many records are in the journal. Abort early if
** the journal is empty.
*/
assert( isOpen(pPager->jfd) );
rc = sqlite3OsFileSize(pPager->jfd, &szJ);
if( rc!=SQLITE_OK || szJ==0 ){
goto end_playback;
}
/* Read the master journal name from the journal, if it is present.
** If a master journal file name is specified, but the file is not
** present on disk, then the journal is not hot and does not need to be
** played back.
**
** TODO: Technically the following is an error because it assumes that
** buffer Pager.pTmpSpace is (mxPathname+1) bytes or larger. i.e. that
** (pPager->pageSize >= pPager->pVfs->mxPathname+1). Using os_unix.c,
** mxPathname is 512, which is the same as the minimum allowable value
** for pageSize.
*/
zMaster = pPager->pTmpSpace;
rc = readMasterJournal(pPager->jfd, zMaster, pPager->pVfs->mxPathname+1);
if( rc==SQLITE_OK && zMaster[0] ){
rc = sqlite3OsAccess(pVfs, zMaster, SQLITE_ACCESS_EXISTS, &res);
}
zMaster = 0;
if( rc!=SQLITE_OK || !res ){
goto end_playback;
}
pPager->journalOff = 0;
needPagerReset = isHot;
/* This loop terminates either when a readJournalHdr() or
** pager_playback_one_page() call returns SQLITE_DONE or an IO error
** occurs.
*/
while( 1 ){
int isUnsync = 0;
/* Read the next journal header from the journal file. If there are
** not enough bytes left in the journal file for a complete header, or
** it is corrupted, then a process must of failed while writing it.
** This indicates nothing more needs to be rolled back.
*/
rc = readJournalHdr(pPager, szJ, &nRec, &mxPg);
if( rc!=SQLITE_OK ){
if( rc==SQLITE_DONE ){
rc = SQLITE_OK;
}
goto end_playback;
}
/* If nRec is 0xffffffff, then this journal was created by a process
** working in no-sync mode. This means that the rest of the journal
** file consists of pages, there are no more journal headers. Compute
** the value of nRec based on this assumption.
*/
if( nRec==0xffffffff ){
assert( pPager->journalOff==JOURNAL_HDR_SZ(pPager) );
nRec = (int)((szJ - JOURNAL_HDR_SZ(pPager))/JOURNAL_PG_SZ(pPager));
}
/* If nRec is 0 and this rollback is of a transaction created by this
** process and if this is the final header in the journal, then it means
** that this part of the journal was being filled but has not yet been
** synced to disk. Compute the number of pages based on the remaining
** size of the file.
**
** The third term of the test was added to fix ticket #2565.
** When rolling back a hot journal, nRec==0 always means that the next
** chunk of the journal contains zero pages to be rolled back. But
** when doing a ROLLBACK and the nRec==0 chunk is the last chunk in
** the journal, it means that the journal might contain additional
** pages that need to be rolled back and that the number of pages
** should be computed based on the journal file size.
*/
testcase( nRec==0 && !isHot
&& pPager->journalHdr+JOURNAL_HDR_SZ(pPager)!=pPager->journalOff
&& ((szJ - pPager->journalOff) / JOURNAL_PG_SZ(pPager))>0
&& pagerNextJournalPageIsValid(pPager)
);
if( nRec==0 && !isHot &&
pPager->journalHdr+JOURNAL_HDR_SZ(pPager)==pPager->journalOff ){
nRec = (int)((szJ - pPager->journalOff) / JOURNAL_PG_SZ(pPager));
isUnsync = 1;
}
/* If this is the first header read from the journal, truncate the
** database file back to its original size.
*/
if( pPager->journalOff==JOURNAL_HDR_SZ(pPager) ){
rc = pager_truncate(pPager, mxPg);
if( rc!=SQLITE_OK ){
goto end_playback;
}
pPager->dbSize = mxPg;
}
/* Copy original pages out of the journal and back into the
** database file and/or page cache.
*/
for(u=0; u<nRec; u++){
if( needPagerReset ){
pager_reset(pPager);
needPagerReset = 0;
}
rc = pager_playback_one_page(pPager,1,isUnsync,&pPager->journalOff,0,0);
if( rc!=SQLITE_OK ){
if( rc==SQLITE_DONE ){
rc = SQLITE_OK;
pPager->journalOff = szJ;
break;
}else{
/* If we are unable to rollback, quit and return the error
** code. This will cause the pager to enter the error state
** so that no further harm will be done. Perhaps the next
** process to come along will be able to rollback the database.
*/
goto end_playback;
}
}
}
}
/*NOTREACHED*/
assert( 0 );
end_playback:
/* Following a rollback, the database file should be back in its original
** state prior to the start of the transaction, so invoke the
** SQLITE_FCNTL_DB_UNCHANGED file-control method to disable the
** assertion that the transaction counter was modified.
*/
assert(
pPager->fd->pMethods==0 ||
sqlite3OsFileControl(pPager->fd,SQLITE_FCNTL_DB_UNCHANGED,0)>=SQLITE_OK
);
/* If this playback is happening automatically as a result of an IO or
** malloc error that occurred after the change-counter was updated but
** before the transaction was committed, then the change-counter
** modification may just have been reverted. If this happens in exclusive
** mode, then subsequent transactions performed by the connection will not
** update the change-counter at all. This may lead to cache inconsistency
** problems for other processes at some point in the future. So, just
** in case this has happened, clear the changeCountDone flag now.
*/
pPager->changeCountDone = pPager->tempFile;
if( rc==SQLITE_OK ){
zMaster = pPager->pTmpSpace;
rc = readMasterJournal(pPager->jfd, zMaster, pPager->pVfs->mxPathname+1);
testcase( rc!=SQLITE_OK );
}
if( rc==SQLITE_OK ){
rc = pager_end_transaction(pPager, zMaster[0]!='\0');
testcase( rc!=SQLITE_OK );
}
if( rc==SQLITE_OK && zMaster[0] && res ){
/* If there was a master journal and this routine will return success,
** see if it is possible to delete the master journal.
*/
rc = pager_delmaster(pPager, zMaster);
testcase( rc!=SQLITE_OK );
}
/* The Pager.sectorSize variable may have been updated while rolling
** back a journal created by a process with a different sector size
** value. Reset it to the correct value for this process.
*/
setSectorSize(pPager);
return rc;
}
/*
** Playback savepoint pSavepoint. Or, if pSavepoint==NULL, then playback
** the entire master journal file. The case pSavepoint==NULL occurs when
** a ROLLBACK TO command is invoked on a SAVEPOINT that is a transaction
** savepoint.
**
** When pSavepoint is not NULL (meaning a non-transaction savepoint is
** being rolled back), then the rollback consists of up to three stages,
** performed in the order specified:
**
** * Pages are played back from the main journal starting at byte
** offset PagerSavepoint.iOffset and continuing to
** PagerSavepoint.iHdrOffset, or to the end of the main journal
** file if PagerSavepoint.iHdrOffset is zero.
**
** * If PagerSavepoint.iHdrOffset is not zero, then pages are played
** back starting from the journal header immediately following
** PagerSavepoint.iHdrOffset to the end of the main journal file.
**
** * Pages are then played back from the sub-journal file, starting
** with the PagerSavepoint.iSubRec and continuing to the end of
** the journal file.
**
** Throughout the rollback process, each time a page is rolled back, the
** corresponding bit is set in a bitvec structure (variable pDone in the
** implementation below). This is used to ensure that a page is only
** rolled back the first time it is encountered in either journal.
**
** If pSavepoint is NULL, then pages are only played back from the main
** journal file. There is no need for a bitvec in this case.
**
** In either case, before playback commences the Pager.dbSize variable
** is reset to the value that it held at the start of the savepoint
** (or transaction). No page with a page-number greater than this value
** is played back. If one is encountered it is simply skipped.
*/
static int pagerPlaybackSavepoint(Pager *pPager, PagerSavepoint *pSavepoint){
i64 szJ; /* Effective size of the main journal */
i64 iHdrOff; /* End of first segment of main-journal records */
int rc = SQLITE_OK; /* Return code */
Bitvec *pDone = 0; /* Bitvec to ensure pages played back only once */
assert( pPager->state>=PAGER_SHARED );
/* Allocate a bitvec to use to store the set of pages rolled back */
if( pSavepoint ){
pDone = sqlite3BitvecCreate(pSavepoint->nOrig);
if( !pDone ){
return SQLITE_NOMEM;
}
}
/* Set the database size back to the value it was before the savepoint
** being reverted was opened.
*/
pPager->dbSize = pSavepoint ? pSavepoint->nOrig : pPager->dbOrigSize;
/* Use pPager->journalOff as the effective size of the main rollback
** journal. The actual file might be larger than this in
** PAGER_JOURNALMODE_TRUNCATE or PAGER_JOURNALMODE_PERSIST. But anything
** past pPager->journalOff is off-limits to us.
*/
szJ = pPager->journalOff;
/* Begin by rolling back records from the main journal starting at
** PagerSavepoint.iOffset and continuing to the next journal header.
** There might be records in the main journal that have a page number
** greater than the current database size (pPager->dbSize) but those
** will be skipped automatically. Pages are added to pDone as they
** are played back.
*/
if( pSavepoint ){
iHdrOff = pSavepoint->iHdrOffset ? pSavepoint->iHdrOffset : szJ;
pPager->journalOff = pSavepoint->iOffset;
while( rc==SQLITE_OK && pPager->journalOff<iHdrOff ){
rc = pager_playback_one_page(pPager, 1, 0, &pPager->journalOff, 1, pDone);
}
assert( rc!=SQLITE_DONE );
}else{
pPager->journalOff = 0;
}
/* Continue rolling back records out of the main journal starting at
** the first journal header seen and continuing until the effective end
** of the main journal file. Continue to skip out-of-range pages and
** continue adding pages rolled back to pDone.
*/
while( rc==SQLITE_OK && pPager->journalOff<szJ ){
u32 ii; /* Loop counter */
u32 nJRec = 0; /* Number of Journal Records */
u32 dummy;
rc = readJournalHdr(pPager, szJ, &nJRec, &dummy);
assert( rc!=SQLITE_DONE );
/*
** The "pPager->journalHdr+JOURNAL_HDR_SZ(pPager)==pPager->journalOff"
** test is related to ticket #2565. See the discussion in the
** pager_playback() function for additional information.
*/
assert( !(nJRec==0
&& pPager->journalHdr+JOURNAL_HDR_SZ(pPager)!=pPager->journalOff
&& ((szJ - pPager->journalOff) / JOURNAL_PG_SZ(pPager))>0
&& pagerNextJournalPageIsValid(pPager))
);
if( nJRec==0
&& pPager->journalHdr+JOURNAL_HDR_SZ(pPager)==pPager->journalOff
){
nJRec = (u32)((szJ - pPager->journalOff)/JOURNAL_PG_SZ(pPager));
}
for(ii=0; rc==SQLITE_OK && ii<nJRec && pPager->journalOff<szJ; ii++){
rc = pager_playback_one_page(pPager, 1, 0, &pPager->journalOff, 1, pDone);
}
assert( rc!=SQLITE_DONE );
}
assert( rc!=SQLITE_OK || pPager->journalOff==szJ );
/* Finally, rollback pages from the sub-journal. Page that were
** previously rolled back out of the main journal (and are hence in pDone)
** will be skipped. Out-of-range pages are also skipped.
*/
if( pSavepoint ){
u32 ii; /* Loop counter */
i64 offset = pSavepoint->iSubRec*(4+pPager->pageSize);
for(ii=pSavepoint->iSubRec; rc==SQLITE_OK && ii<pPager->nSubRec; ii++){
assert( offset==ii*(4+pPager->pageSize) );
rc = pager_playback_one_page(pPager, 0, 0, &offset, 1, pDone);
}
assert( rc!=SQLITE_DONE );
}
sqlite3BitvecDestroy(pDone);
if( rc==SQLITE_OK ){
pPager->journalOff = szJ;
}
return rc;
}
/*
** Change the maximum number of in-memory pages that are allowed.
*/
void sqlite3PagerSetCachesize(Pager *pPager, int mxPage){
sqlite3PcacheSetCachesize(pPager->pPCache, mxPage);
}
/*
** Adjust the robustness of the database to damage due to OS crashes
** or power failures by changing the number of syncs()s when writing
** the rollback journal. There are three levels:
**
** OFF sqlite3OsSync() is never called. This is the default
** for temporary and transient files.
**
** NORMAL The journal is synced once before writes begin on the
** database. This is normally adequate protection, but
** it is theoretically possible, though very unlikely,
** that an inopertune power failure could leave the journal
** in a state which would cause damage to the database
** when it is rolled back.
**
** FULL The journal is synced twice before writes begin on the
** database (with some additional information - the nRec field
** of the journal header - being written in between the two
** syncs). If we assume that writing a
** single disk sector is atomic, then this mode provides
** assurance that the journal will not be corrupted to the
** point of causing damage to the database during rollback.
**
** Numeric values associated with these states are OFF==1, NORMAL=2,
** and FULL=3.
*/
#ifndef SQLITE_OMIT_PAGER_PRAGMAS
void sqlite3PagerSetSafetyLevel(Pager *pPager, int level, int bFullFsync){
pPager->noSync = (level==1 || pPager->tempFile) ?1:0;
pPager->fullSync = (level==3 && !pPager->tempFile) ?1:0;
pPager->sync_flags = (bFullFsync?SQLITE_SYNC_FULL:SQLITE_SYNC_NORMAL);
if( pPager->noSync ) pPager->needSync = 0;
}
#endif
/*
** The following global variable is incremented whenever the library
** attempts to open a temporary file. This information is used for
** testing and analysis only.
*/
#ifdef SQLITE_TEST
int sqlite3_opentemp_count = 0;
#endif
/*
** Open a temporary file.
**
** Write the file descriptor into *pFile. Return SQLITE_OK on success
** or some other error code if we fail. The OS will automatically
** delete the temporary file when it is closed.
**
** The flags passed to the VFS layer xOpen() call are those specified
** by parameter vfsFlags ORed with the following:
**
** SQLITE_OPEN_READWRITE
** SQLITE_OPEN_CREATE
** SQLITE_OPEN_EXCLUSIVE
** SQLITE_OPEN_DELETEONCLOSE
*/
static int pagerOpentemp(
Pager *pPager, /* The pager object */
sqlite3_file *pFile, /* Write the file descriptor here */
int vfsFlags /* Flags passed through to the VFS */
){
int rc; /* Return code */
#ifdef SQLITE_TEST
sqlite3_opentemp_count++; /* Used for testing and analysis only */
#endif
vfsFlags |= SQLITE_OPEN_READWRITE | SQLITE_OPEN_CREATE |
SQLITE_OPEN_EXCLUSIVE | SQLITE_OPEN_DELETEONCLOSE;
rc = sqlite3OsOpen(pPager->pVfs, 0, pFile, vfsFlags, 0);
assert( rc!=SQLITE_OK || isOpen(pFile) );
return rc;
}
/*
** Set the busy handler function.
**
** The pager invokes the busy-handler if sqlite3OsLock() returns
** SQLITE_BUSY when trying to upgrade from no-lock to a SHARED lock,
** or when trying to upgrade from a RESERVED lock to an EXCLUSIVE
** lock. It does *not* invoke the busy handler when upgrading from
** SHARED to RESERVED, or when upgrading from SHARED to EXCLUSIVE
** (which occurs during hot-journal rollback). Summary:
**
** Transition | Invokes xBusyHandler
** --------------------------------------------------------
** NO_LOCK -> SHARED_LOCK | Yes
** SHARED_LOCK -> RESERVED_LOCK | No
** SHARED_LOCK -> EXCLUSIVE_LOCK | No
** RESERVED_LOCK -> EXCLUSIVE_LOCK | Yes
**
** If the busy-handler callback returns non-zero, the lock is
** retried. If it returns zero, then the SQLITE_BUSY error is
** returned to the caller of the pager API function.
*/
void sqlite3PagerSetBusyhandler(
Pager *pPager, /* Pager object */
int (*xBusyHandler)(void *), /* Pointer to busy-handler function */
void *pBusyHandlerArg /* Argument to pass to xBusyHandler */
){
pPager->xBusyHandler = xBusyHandler;
pPager->pBusyHandlerArg = pBusyHandlerArg;
}
/*
** Set the reinitializer for this pager. If not NULL, the reinitializer
** is called when the content of a page in cache is modified (restored)
** as part of a transaction or savepoint rollback. The callback gives
** higher-level code an opportunity to restore the EXTRA section to
** agree with the restored page data.
*/
void sqlite3PagerSetReiniter(Pager *pPager, void (*xReinit)(DbPage*)){
pPager->xReiniter = xReinit;
}
/*
** Change the page size used by the Pager object. The new page size
** is passed in *pPageSize.
**
** If the pager is in the error state when this function is called, it
** is a no-op. The value returned is the error state error code (i.e.
** one of SQLITE_IOERR, SQLITE_CORRUPT or SQLITE_FULL).
**
** Otherwise, if all of the following are true:
**
** * the new page size (value of *pPageSize) is valid (a power
** of two between 512 and SQLITE_MAX_PAGE_SIZE, inclusive), and
**
** * there are no outstanding page references, and
**
** * the database is either not an in-memory database or it is
** an in-memory database that currently consists of zero pages.
**
** then the pager object page size is set to *pPageSize.
**
** If the page size is changed, then this function uses sqlite3PagerMalloc()
** to obtain a new Pager.pTmpSpace buffer. If this allocation attempt
** fails, SQLITE_NOMEM is returned and the page size remains unchanged.
** In all other cases, SQLITE_OK is returned.
**
** If the page size is not changed, either because one of the enumerated
** conditions above is not true, the pager was in error state when this
** function was called, or because the memory allocation attempt failed,
** then *pPageSize is set to the old, retained page size before returning.
*/
int sqlite3PagerSetPagesize(Pager *pPager, u16 *pPageSize){
int rc = pPager->errCode;
if( rc==SQLITE_OK ){
u16 pageSize = *pPageSize;
assert( pageSize==0 || (pageSize>=512 && pageSize<=SQLITE_MAX_PAGE_SIZE) );
if( pageSize && pageSize!=pPager->pageSize
&& (pPager->memDb==0 || pPager->dbSize==0)
&& sqlite3PcacheRefCount(pPager->pPCache)==0
){
char *pNew = (char *)sqlite3PageMalloc(pageSize);
if( !pNew ){
rc = SQLITE_NOMEM;
}else{
pager_reset(pPager);
pPager->pageSize = pageSize;
sqlite3PageFree(pPager->pTmpSpace);
pPager->pTmpSpace = pNew;
sqlite3PcacheSetPageSize(pPager->pPCache, pageSize);
}
}
*pPageSize = (u16)pPager->pageSize;
}
return rc;
}
/*
** Return a pointer to the "temporary page" buffer held internally
** by the pager. This is a buffer that is big enough to hold the
** entire content of a database page. This buffer is used internally
** during rollback and will be overwritten whenever a rollback
** occurs. But other modules are free to use it too, as long as
** no rollbacks are happening.
*/
void *sqlite3PagerTempSpace(Pager *pPager){
return pPager->pTmpSpace;
}
/*
** Attempt to set the maximum database page count if mxPage is positive.
** Make no changes if mxPage is zero or negative. And never reduce the
** maximum page count below the current size of the database.
**
** Regardless of mxPage, return the current maximum page count.
*/
int sqlite3PagerMaxPageCount(Pager *pPager, int mxPage){
if( mxPage>0 ){
pPager->mxPgno = mxPage;
}
sqlite3PagerPagecount(pPager, 0);
return pPager->mxPgno;
}
/*
** The following set of routines are used to disable the simulated
** I/O error mechanism. These routines are used to avoid simulated
** errors in places where we do not care about errors.
**
** Unless -DSQLITE_TEST=1 is used, these routines are all no-ops
** and generate no code.
*/
#ifdef SQLITE_TEST
extern int sqlite3_io_error_pending;
extern int sqlite3_io_error_hit;
static int saved_cnt;
void disable_simulated_io_errors(void){
saved_cnt = sqlite3_io_error_pending;
sqlite3_io_error_pending = -1;
}
void enable_simulated_io_errors(void){
sqlite3_io_error_pending = saved_cnt;
}
#else
# define disable_simulated_io_errors()
# define enable_simulated_io_errors()
#endif
/*
** Read the first N bytes from the beginning of the file into memory
** that pDest points to.
**
** If the pager was opened on a transient file (zFilename==""), or
** opened on a file less than N bytes in size, the output buffer is
** zeroed and SQLITE_OK returned. The rationale for this is that this
** function is used to read database headers, and a new transient or
** zero sized database has a header than consists entirely of zeroes.
**
** If any IO error apart from SQLITE_IOERR_SHORT_READ is encountered,
** the error code is returned to the caller and the contents of the
** output buffer undefined.
*/
int sqlite3PagerReadFileheader(Pager *pPager, int N, unsigned char *pDest){
int rc = SQLITE_OK;
memset(pDest, 0, N);
assert( isOpen(pPager->fd) || pPager->tempFile );
if( isOpen(pPager->fd) ){
IOTRACE(("DBHDR %p 0 %d\n", pPager, N))
rc = sqlite3OsRead(pPager->fd, pDest, N, 0);
if( rc==SQLITE_IOERR_SHORT_READ ){
rc = SQLITE_OK;
}
}
return rc;
}
/*
** Return the total number of pages in the database file associated
** with pPager. Normally, this is calculated as (<db file size>/<page-size>).
** However, if the file is between 1 and <page-size> bytes in size, then
** this is considered a 1 page file.
**
** If the pager is in error state when this function is called, then the
** error state error code is returned and *pnPage left unchanged. Or,
** if the file system has to be queried for the size of the file and
** the query attempt returns an IO error, the IO error code is returned
** and *pnPage is left unchanged.
**
** Otherwise, if everything is successful, then SQLITE_OK is returned
** and *pnPage is set to the number of pages in the database.
*/
int sqlite3PagerPagecount(Pager *pPager, int *pnPage){
Pgno nPage; /* Value to return via *pnPage */
/* If the pager is already in the error state, return the error code. */
if( pPager->errCode ){
return pPager->errCode;
}
/* Determine the number of pages in the file. Store this in nPage. */
if( pPager->dbSizeValid ){
nPage = pPager->dbSize;
}else{
int rc; /* Error returned by OsFileSize() */
i64 n = 0; /* File size in bytes returned by OsFileSize() */
assert( isOpen(pPager->fd) || pPager->tempFile );
if( isOpen(pPager->fd) && (0 != (rc = sqlite3OsFileSize(pPager->fd, &n))) ){
pager_error(pPager, rc);
return rc;
}
if( n>0 && n<pPager->pageSize ){
nPage = 1;
}else{
nPage = (Pgno)(n / pPager->pageSize);
}
if( pPager->state!=PAGER_UNLOCK ){
pPager->dbSize = nPage;
pPager->dbFileSize = nPage;
pPager->dbSizeValid = 1;
}
}
/* If the current number of pages in the file is greater than the
** configured maximum pager number, increase the allowed limit so
** that the file can be read.
*/
if( nPage>pPager->mxPgno ){
pPager->mxPgno = (Pgno)nPage;
}
/* Set the output variable and return SQLITE_OK */
if( pnPage ){
*pnPage = nPage;
}
return SQLITE_OK;
}
/*
** Try to obtain a lock of type locktype on the database file. If
** a similar or greater lock is already held, this function is a no-op
** (returning SQLITE_OK immediately).
**
** Otherwise, attempt to obtain the lock using sqlite3OsLock(). Invoke
** the busy callback if the lock is currently not available. Repeat
** until the busy callback returns false or until the attempt to
** obtain the lock succeeds.
**
** Return SQLITE_OK on success and an error code if we cannot obtain
** the lock. If the lock is obtained successfully, set the Pager.state
** variable to locktype before returning.
*/
static int pager_wait_on_lock(Pager *pPager, int locktype){
int rc; /* Return code */
/* The OS lock values must be the same as the Pager lock values */
assert( PAGER_SHARED==SHARED_LOCK );
assert( PAGER_RESERVED==RESERVED_LOCK );
assert( PAGER_EXCLUSIVE==EXCLUSIVE_LOCK );
/* If the file is currently unlocked then the size must be unknown */
assert( pPager->state>=PAGER_SHARED || pPager->dbSizeValid==0 );
/* Check that this is either a no-op (because the requested lock is
** already held, or one of the transistions that the busy-handler
** may be invoked during, according to the comment above
** sqlite3PagerSetBusyhandler().
*/
assert( (pPager->state>=locktype)
|| (pPager->state==PAGER_UNLOCK && locktype==PAGER_SHARED)
|| (pPager->state==PAGER_RESERVED && locktype==PAGER_EXCLUSIVE)
);
if( pPager->state>=locktype ){
rc = SQLITE_OK;
}else{
do {
rc = sqlite3OsLock(pPager->fd, locktype);
}while( rc==SQLITE_BUSY && pPager->xBusyHandler(pPager->pBusyHandlerArg) );
if( rc==SQLITE_OK ){
pPager->state = (u8)locktype;
IOTRACE(("LOCK %p %d\n", pPager, locktype))
}
}
return rc;
}
/*
** Truncate the in-memory database file image to nPage pages. This
** function does not actually modify the database file on disk. It
** just sets the internal state of the pager object so that the
** truncation will be done when the current transaction is committed.
*/
void sqlite3PagerTruncateImage(Pager *pPager, Pgno nPage){
assert( pPager->dbSizeValid );
assert( pPager->dbSize>=nPage );
assert( pPager->state>=PAGER_RESERVED );
pPager->dbSize = nPage;
}
/*
** Shutdown the page cache. Free all memory and close all files.
**
** If a transaction was in progress when this routine is called, that
** transaction is rolled back. All outstanding pages are invalidated
** and their memory is freed. Any attempt to use a page associated
** with this page cache after this function returns will likely
** result in a coredump.
**
** This function always succeeds. If a transaction is active an attempt
** is made to roll it back. If an error occurs during the rollback
** a hot journal may be left in the filesystem but no error is returned
** to the caller.
*/
int sqlite3PagerClose(Pager *pPager){
disable_simulated_io_errors();
sqlite3BeginBenignMalloc();
pPager->errCode = 0;
pPager->exclusiveMode = 0;
pager_reset(pPager);
if( MEMDB ){
pager_unlock(pPager);
}else{
/* Set Pager.journalHdr to -1 for the benefit of the pager_playback()
** call which may be made from within pagerUnlockAndRollback(). If it
** is not -1, then the unsynced portion of an open journal file may
** be played back into the database. If a power failure occurs while
** this is happening, the database may become corrupt.
*/
pPager->journalHdr = -1;
pagerUnlockAndRollback(pPager);
}
sqlite3EndBenignMalloc();
enable_simulated_io_errors();
PAGERTRACE(("CLOSE %d\n", PAGERID(pPager)));
IOTRACE(("CLOSE %p\n", pPager))
sqlite3OsClose(pPager->fd);
sqlite3PageFree(pPager->pTmpSpace);
sqlite3PcacheClose(pPager->pPCache);
assert( !pPager->aSavepoint && !pPager->pInJournal );
assert( !isOpen(pPager->jfd) && !isOpen(pPager->sjfd) );
sqlite3_free(pPager);
return SQLITE_OK;
}
#if !defined(NDEBUG) || defined(SQLITE_TEST)
/*
** Return the page number for page pPg.
*/
Pgno sqlite3PagerPagenumber(DbPage *pPg){
return pPg->pgno;
}
#endif
/*
** Increment the reference count for page pPg.
*/
void sqlite3PagerRef(DbPage *pPg){
sqlite3PcacheRef(pPg);
}
/*
** Sync the journal. In other words, make sure all the pages that have
** been written to the journal have actually reached the surface of the
** disk and can be restored in the event of a hot-journal rollback.
**
** If the Pager.needSync flag is not set, then this function is a
** no-op. Otherwise, the actions required depend on the journal-mode
** and the device characteristics of the the file-system, as follows:
**
** * If the journal file is an in-memory journal file, no action need
** be taken.
**
** * Otherwise, if the device does not support the SAFE_APPEND property,
** then the nRec field of the most recently written journal header
** is updated to contain the number of journal records that have
** been written following it. If the pager is operating in full-sync
** mode, then the journal file is synced before this field is updated.
**
** * If the device does not support the SEQUENTIAL property, then
** journal file is synced.
**
** Or, in pseudo-code:
**
** if( NOT <in-memory journal> ){
** if( NOT SAFE_APPEND ){
** if( <full-sync mode> ) xSync(<journal file>);
** <update nRec field>
** }
** if( NOT SEQUENTIAL ) xSync(<journal file>);
** }
**
** The Pager.needSync flag is never be set for temporary files, or any
** file operating in no-sync mode (Pager.noSync set to non-zero).
**
** If successful, this routine clears the PGHDR_NEED_SYNC flag of every
** page currently held in memory before returning SQLITE_OK. If an IO
** error is encountered, then the IO error code is returned to the caller.
*/
static int syncJournal(Pager *pPager){
if( pPager->needSync ){
assert( !pPager->tempFile );
if( pPager->journalMode!=PAGER_JOURNALMODE_MEMORY ){
int rc; /* Return code */
const int iDc = sqlite3OsDeviceCharacteristics(pPager->fd);
assert( isOpen(pPager->jfd) );
if( 0==(iDc&SQLITE_IOCAP_SAFE_APPEND) ){
/* Variable iNRecOffset is set to the offset in the journal file
** of the nRec field of the most recently written journal header.
** This field will be updated following the xSync() operation
** on the journal file. */
i64 iNRecOffset = pPager->journalHdr + sizeof(aJournalMagic);
/* This block deals with an obscure problem. If the last connection
** that wrote to this database was operating in persistent-journal
** mode, then the journal file may at this point actually be larger
** than Pager.journalOff bytes. If the next thing in the journal
** file happens to be a journal-header (written as part of the
** previous connections transaction), and a crash or power-failure
** occurs after nRec is updated but before this connection writes
** anything else to the journal file (or commits/rolls back its
** transaction), then SQLite may become confused when doing the
** hot-journal rollback following recovery. It may roll back all
** of this connections data, then proceed to rolling back the old,
** out-of-date data that follows it. Database corruption.
**
** To work around this, if the journal file does appear to contain
** a valid header following Pager.journalOff, then write a 0x00
** byte to the start of it to prevent it from being recognized.
**
** Variable iNextHdrOffset is set to the offset at which this
** problematic header will occur, if it exists. aMagic is used
** as a temporary buffer to inspect the first couple of bytes of
** the potential journal header.
*/
i64 iNextHdrOffset = journalHdrOffset(pPager);
u8 aMagic[8];
rc = sqlite3OsRead(pPager->jfd, aMagic, 8, iNextHdrOffset);
if( rc==SQLITE_OK && 0==memcmp(aMagic, aJournalMagic, 8) ){
static const u8 zerobyte = 0;
rc = sqlite3OsWrite(pPager->jfd, &zerobyte, 1, iNextHdrOffset);
}
if( rc!=SQLITE_OK && rc!=SQLITE_IOERR_SHORT_READ ){
return rc;
}
/* Write the nRec value into the journal file header. If in
** full-synchronous mode, sync the journal first. This ensures that
** all data has really hit the disk before nRec is updated to mark
** it as a candidate for rollback.
**
** This is not required if the persistent media supports the
** SAFE_APPEND property. Because in this case it is not possible
** for garbage data to be appended to the file, the nRec field
** is populated with 0xFFFFFFFF when the journal header is written
** and never needs to be updated.
*/
if( pPager->fullSync && 0==(iDc&SQLITE_IOCAP_SEQUENTIAL) ){
PAGERTRACE(("SYNC journal of %d\n", PAGERID(pPager)));
IOTRACE(("JSYNC %p\n", pPager))
rc = sqlite3OsSync(pPager->jfd, pPager->sync_flags);
if( rc!=SQLITE_OK ) return rc;
}
IOTRACE(("JHDR %p %lld %d\n", pPager, iNRecOffset, 4));
rc = write32bits(pPager->jfd, iNRecOffset, pPager->nRec);
if( rc!=SQLITE_OK ) return rc;
}
if( 0==(iDc&SQLITE_IOCAP_SEQUENTIAL) ){
PAGERTRACE(("SYNC journal of %d\n", PAGERID(pPager)));
IOTRACE(("JSYNC %p\n", pPager))
rc = sqlite3OsSync(pPager->jfd, pPager->sync_flags|
(pPager->sync_flags==SQLITE_SYNC_FULL?SQLITE_SYNC_DATAONLY:0)
);
if( rc!=SQLITE_OK ) return rc;
}
}
/* The journal file was just successfully synced. Set Pager.needSync
** to zero and clear the PGHDR_NEED_SYNC flag on all pagess.
*/
pPager->needSync = 0;
pPager->journalStarted = 1;
sqlite3PcacheClearSyncFlags(pPager->pPCache);
}
return SQLITE_OK;
}
/*
** The argument is the first in a linked list of dirty pages connected
** by the PgHdr.pDirty pointer. This function writes each one of the
** in-memory pages in the list to the database file. The argument may
** be NULL, representing an empty list. In this case this function is
** a no-op.
**
** The pager must hold at least a RESERVED lock when this function
** is called. Before writing anything to the database file, this lock
** is upgraded to an EXCLUSIVE lock. If the lock cannot be obtained,
** SQLITE_BUSY is returned and no data is written to the database file.
**
** If the pager is a temp-file pager and the actual file-system file
** is not yet open, it is created and opened before any data is
** written out.
**
** Once the lock has been upgraded and, if necessary, the file opened,
** the pages are written out to the database file in list order. Writing
** a page is skipped if it meets either of the following criteria:
**
** * The page number is greater than Pager.dbSize, or
** * The PGHDR_DONT_WRITE flag is set on the page.
**
** If writing out a page causes the database file to grow, Pager.dbFileSize
** is updated accordingly. If page 1 is written out, then the value cached
** in Pager.dbFileVers[] is updated to match the new value stored in
** the database file.
**
** If everything is successful, SQLITE_OK is returned. If an IO error
** occurs, an IO error code is returned. Or, if the EXCLUSIVE lock cannot
** be obtained, SQLITE_BUSY is returned.
*/
static int pager_write_pagelist(PgHdr *pList){
Pager *pPager; /* Pager object */
int rc; /* Return code */
if( pList==0 ) return SQLITE_OK;
pPager = pList->pPager;
/* At this point there may be either a RESERVED or EXCLUSIVE lock on the
** database file. If there is already an EXCLUSIVE lock, the following
** call is a no-op.
**
** Moving the lock from RESERVED to EXCLUSIVE actually involves going
** through an intermediate state PENDING. A PENDING lock prevents new
** readers from attaching to the database but is unsufficient for us to
** write. The idea of a PENDING lock is to prevent new readers from
** coming in while we wait for existing readers to clear.
**
** While the pager is in the RESERVED state, the original database file
** is unchanged and we can rollback without having to playback the
** journal into the original database file. Once we transition to
** EXCLUSIVE, it means the database file has been changed and any rollback
** will require a journal playback.
*/
assert( pPager->state>=PAGER_RESERVED );
rc = pager_wait_on_lock(pPager, EXCLUSIVE_LOCK);
/* If the file is a temp-file has not yet been opened, open it now. It
** is not possible for rc to be other than SQLITE_OK if this branch
** is taken, as pager_wait_on_lock() is a no-op for temp-files.
*/
if( !isOpen(pPager->fd) ){
assert( pPager->tempFile && rc==SQLITE_OK );
rc = pagerOpentemp(pPager, pPager->fd, pPager->vfsFlags);
}
while( rc==SQLITE_OK && pList ){
Pgno pgno = pList->pgno;
/* If there are dirty pages in the page cache with page numbers greater
** than Pager.dbSize, this means sqlite3PagerTruncateImage() was called to
** make the file smaller (presumably by auto-vacuum code). Do not write
** any such pages to the file.
**
** Also, do not write out any page that has the PGHDR_DONT_WRITE flag
** set (set by sqlite3PagerDontWrite()).
*/
if( pgno<=pPager->dbSize && 0==(pList->flags&PGHDR_DONT_WRITE) ){
i64 offset = (pgno-1)*(i64)pPager->pageSize; /* Offset to write */
char *pData = CODEC2(pPager, pList->pData, pgno, 6); /* Data to write */
/* Write out the page data. */
rc = sqlite3OsWrite(pPager->fd, pData, pPager->pageSize, offset);
/* If page 1 was just written, update Pager.dbFileVers to match
** the value now stored in the database file. If writing this
** page caused the database file to grow, update dbFileSize.
*/
if( pgno==1 ){
memcpy(&pPager->dbFileVers, &pData[24], sizeof(pPager->dbFileVers));
}
if( pgno>pPager->dbFileSize ){
pPager->dbFileSize = pgno;
}
/* Update any backup objects copying the contents of this pager. */
sqlite3BackupUpdate(pPager->pBackup, pgno, (u8 *)pData);
PAGERTRACE(("STORE %d page %d hash(%08x)\n",
PAGERID(pPager), pgno, pager_pagehash(pList)));
IOTRACE(("PGOUT %p %d\n", pPager, pgno));
PAGER_INCR(sqlite3_pager_writedb_count);
PAGER_INCR(pPager->nWrite);
}else{
PAGERTRACE(("NOSTORE %d page %d\n", PAGERID(pPager), pgno));
}
#ifdef SQLITE_CHECK_PAGES
pList->pageHash = pager_pagehash(pList);
#endif
pList = pList->pDirty;
}
return rc;
}
/*
** Append a record of the current state of page pPg to the sub-journal.
** It is the callers responsibility to use subjRequiresPage() to check
** that it is really required before calling this function.
**
** If successful, set the bit corresponding to pPg->pgno in the bitvecs
** for all open savepoints before returning.
**
** This function returns SQLITE_OK if everything is successful, an IO
** error code if the attempt to write to the sub-journal fails, or
** SQLITE_NOMEM if a malloc fails while setting a bit in a savepoint
** bitvec.
*/
static int subjournalPage(PgHdr *pPg){
int rc = SQLITE_OK;
Pager *pPager = pPg->pPager;
if( isOpen(pPager->sjfd) ){
void *pData = pPg->pData;
i64 offset = pPager->nSubRec*(4+pPager->pageSize);
char *pData2 = CODEC2(pPager, pData, pPg->pgno, 7);
PAGERTRACE(("STMT-JOURNAL %d page %d\n", PAGERID(pPager), pPg->pgno));
assert( pageInJournal(pPg) || pPg->pgno>pPager->dbOrigSize );
rc = write32bits(pPager->sjfd, offset, pPg->pgno);
if( rc==SQLITE_OK ){
rc = sqlite3OsWrite(pPager->sjfd, pData2, pPager->pageSize, offset+4);
}
}
if( rc==SQLITE_OK ){
pPager->nSubRec++;
assert( pPager->nSavepoint>0 );
rc = addToSavepointBitvecs(pPager, pPg->pgno);
testcase( rc!=SQLITE_OK );
}
return rc;
}
/*
** This function is called by the pcache layer when it has reached some
** soft memory limit. The first argument is a pointer to a Pager object
** (cast as a void*). The pager is always 'purgeable' (not an in-memory
** database). The second argument is a reference to a page that is
** currently dirty but has no outstanding references. The page
** is always associated with the Pager object passed as the first
** argument.
**
** The job of this function is to make pPg clean by writing its contents
** out to the database file, if possible. This may involve syncing the
** journal file.
**
** If successful, sqlite3PcacheMakeClean() is called on the page and
** SQLITE_OK returned. If an IO error occurs while trying to make the
** page clean, the IO error code is returned. If the page cannot be
** made clean for some other reason, but no error occurs, then SQLITE_OK
** is returned by sqlite3PcacheMakeClean() is not called.
*/
static int pagerStress(void *p, PgHdr *pPg){
Pager *pPager = (Pager *)p;
int rc = SQLITE_OK;
assert( pPg->pPager==pPager );
assert( pPg->flags&PGHDR_DIRTY );
/* The doNotSync flag is set by the sqlite3PagerWrite() function while it
** is journalling a set of two or more database pages that are stored
** on the same disk sector. Syncing the journal is not allowed while
** this is happening as it is important that all members of such a
** set of pages are synced to disk together. So, if the page this function
** is trying to make clean will require a journal sync and the doNotSync
** flag is set, return without doing anything. The pcache layer will
** just have to go ahead and allocate a new page buffer instead of
** reusing pPg.
**
** Similarly, if the pager has already entered the error state, do not
** try to write the contents of pPg to disk.
*/
if( pPager->errCode || (pPager->doNotSync && pPg->flags&PGHDR_NEED_SYNC) ){
return SQLITE_OK;
}
/* Sync the journal file if required. */
if( pPg->flags&PGHDR_NEED_SYNC ){
rc = syncJournal(pPager);
if( rc==SQLITE_OK && pPager->fullSync &&
!(pPager->journalMode==PAGER_JOURNALMODE_MEMORY) &&
!(sqlite3OsDeviceCharacteristics(pPager->fd)&SQLITE_IOCAP_SAFE_APPEND)
){
pPager->nRec = 0;
rc = writeJournalHdr(pPager);
}
}
/* If the page number of this page is larger than the current size of
** the database image, it may need to be written to the sub-journal.
** This is because the call to pager_write_pagelist() below will not
** actually write data to the file in this case.
**
** Consider the following sequence of events:
**
** BEGIN;
** <journal page X>
** <modify page X>
** SAVEPOINT sp;
** <shrink database file to Y pages>
** pagerStress(page X)
** ROLLBACK TO sp;
**
** If (X>Y), then when pagerStress is called page X will not be written
** out to the database file, but will be dropped from the cache. Then,
** following the "ROLLBACK TO sp" statement, reading page X will read
** data from the database file. This will be the copy of page X as it
** was when the transaction started, not as it was when "SAVEPOINT sp"
** was executed.
**
** The solution is to write the current data for page X into the
** sub-journal file now (if it is not already there), so that it will
** be restored to its current value when the "ROLLBACK TO sp" is
** executed.
*/
if( rc==SQLITE_OK && pPg->pgno>pPager->dbSize && subjRequiresPage(pPg) ){
rc = subjournalPage(pPg);
}
/* Write the contents of the page out to the database file. */
if( rc==SQLITE_OK ){
pPg->pDirty = 0;
rc = pager_write_pagelist(pPg);
}
/* Mark the page as clean. */
if( rc==SQLITE_OK ){
PAGERTRACE(("STRESS %d page %d\n", PAGERID(pPager), pPg->pgno));
sqlite3PcacheMakeClean(pPg);
}
return pager_error(pPager, rc);
}
/*
** Allocate and initialize a new Pager object and put a pointer to it
** in *ppPager. The pager should eventually be freed by passing it
** to sqlite3PagerClose().
**
** The zFilename argument is the path to the database file to open.
** If zFilename is NULL then a randomly-named temporary file is created
** and used as the file to be cached. Temporary files are be deleted
** automatically when they are closed. If zFilename is ":memory:" then
** all information is held in cache. It is never written to disk.
** This can be used to implement an in-memory database.
**
** The nExtra parameter specifies the number of bytes of space allocated
** along with each page reference. This space is available to the user
** via the sqlite3PagerGetExtra() API.
**
** The flags argument is used to specify properties that affect the
** operation of the pager. It should be passed some bitwise combination
** of the PAGER_OMIT_JOURNAL and PAGER_NO_READLOCK flags.
**
** The vfsFlags parameter is a bitmask to pass to the flags parameter
** of the xOpen() method of the supplied VFS when opening files.
**
** If the pager object is allocated and the specified file opened
** successfully, SQLITE_OK is returned and *ppPager set to point to
** the new pager object. If an error occurs, *ppPager is set to NULL
** and error code returned. This function may return SQLITE_NOMEM
** (sqlite3Malloc() is used to allocate memory), SQLITE_CANTOPEN or
** various SQLITE_IO_XXX errors.
*/
int sqlite3PagerOpen(
sqlite3_vfs *pVfs, /* The virtual file system to use */
Pager **ppPager, /* OUT: Return the Pager structure here */
const char *zFilename, /* Name of the database file to open */
int nExtra, /* Extra bytes append to each in-memory page */
int flags, /* flags controlling this file */
int vfsFlags /* flags passed through to sqlite3_vfs.xOpen() */
){
u8 *pPtr;
Pager *pPager = 0; /* Pager object to allocate and return */
int rc = SQLITE_OK; /* Return code */
int tempFile = 0; /* True for temp files (incl. in-memory files) */
int memDb = 0; /* True if this is an in-memory file */
int readOnly = 0; /* True if this is a read-only file */
int journalFileSize; /* Bytes to allocate for each journal fd */
char *zPathname = 0; /* Full path to database file */
int nPathname = 0; /* Number of bytes in zPathname */
int useJournal = (flags & PAGER_OMIT_JOURNAL)==0; /* False to omit journal */
int noReadlock = (flags & PAGER_NO_READLOCK)!=0; /* True to omit read-lock */
int pcacheSize = sqlite3PcacheSize(); /* Bytes to allocate for PCache */
u16 szPageDflt = SQLITE_DEFAULT_PAGE_SIZE; /* Default page size */
/* Figure out how much space is required for each journal file-handle
** (there are two of them, the main journal and the sub-journal). This
** is the maximum space required for an in-memory journal file handle
** and a regular journal file-handle. Note that a "regular journal-handle"
** may be a wrapper capable of caching the first portion of the journal
** file in memory to implement the atomic-write optimization (see
** source file journal.c).
*/
if( sqlite3JournalSize(pVfs)>sqlite3MemJournalSize() ){
journalFileSize = ROUND8(sqlite3JournalSize(pVfs));
}else{
journalFileSize = ROUND8(sqlite3MemJournalSize());
}
/* Set the output variable to NULL in case an error occurs. */
*ppPager = 0;
/* Compute and store the full pathname in an allocated buffer pointed
** to by zPathname, length nPathname. Or, if this is a temporary file,
** leave both nPathname and zPathname set to 0.
*/
if( zFilename && zFilename[0] ){
nPathname = pVfs->mxPathname+1;
zPathname = sqlite3Malloc(nPathname*2);
if( zPathname==0 ){
return SQLITE_NOMEM;
}
#ifndef SQLITE_OMIT_MEMORYDB
if( strcmp(zFilename,":memory:")==0 ){
memDb = 1;
zPathname[0] = 0;
}else
#endif
{
zPathname[0] = 0; /* Make sure initialized even if FullPathname() fails */
rc = sqlite3OsFullPathname(pVfs, zFilename, nPathname, zPathname);
}
nPathname = sqlite3Strlen30(zPathname);
if( rc==SQLITE_OK && nPathname+8>pVfs->mxPathname ){
/* This branch is taken when the journal path required by
** the database being opened will be more than pVfs->mxPathname
** bytes in length. This means the database cannot be opened,
** as it will not be possible to open the journal file or even
** check for a hot-journal before reading.
*/
rc = SQLITE_CANTOPEN;
}
if( rc!=SQLITE_OK ){
sqlite3_free(zPathname);
return rc;
}
}
/* Allocate memory for the Pager structure, PCache object, the
** three file descriptors, the database file name and the journal
** file name. The layout in memory is as follows:
**
** Pager object (sizeof(Pager) bytes)
** PCache object (sqlite3PcacheSize() bytes)
** Database file handle (pVfs->szOsFile bytes)
** Sub-journal file handle (journalFileSize bytes)
** Main journal file handle (journalFileSize bytes)
** Database file name (nPathname+1 bytes)
** Journal file name (nPathname+8+1 bytes)
*/
pPtr = (u8 *)sqlite3MallocZero(
ROUND8(sizeof(*pPager)) + /* Pager structure */
ROUND8(pcacheSize) + /* PCache object */
ROUND8(pVfs->szOsFile) + /* The main db file */
journalFileSize * 2 + /* The two journal files */
nPathname + 1 + /* zFilename */
nPathname + 8 + 1 /* zJournal */
);
assert( EIGHT_BYTE_ALIGNMENT(SQLITE_INT_TO_PTR(journalFileSize)) );
if( !pPtr ){
sqlite3_free(zPathname);
return SQLITE_NOMEM;
}
pPager = (Pager*)(pPtr);
pPager->pPCache = (PCache*)(pPtr += ROUND8(sizeof(*pPager)));
pPager->fd = (sqlite3_file*)(pPtr += ROUND8(pcacheSize));
pPager->sjfd = (sqlite3_file*)(pPtr += ROUND8(pVfs->szOsFile));
pPager->jfd = (sqlite3_file*)(pPtr += journalFileSize);
pPager->zFilename = (char*)(pPtr += journalFileSize);
assert( EIGHT_BYTE_ALIGNMENT(pPager->jfd) );
/* Fill in the Pager.zFilename and Pager.zJournal buffers, if required. */
if( zPathname ){
pPager->zJournal = (char*)(pPtr += nPathname + 1);
memcpy(pPager->zFilename, zPathname, nPathname);
memcpy(pPager->zJournal, zPathname, nPathname);
memcpy(&pPager->zJournal[nPathname], "-journal", 8);
sqlite3_free(zPathname);
}
pPager->pVfs = pVfs;
pPager->vfsFlags = vfsFlags;
/* Open the pager file.
*/
if( zFilename && zFilename[0] && !memDb ){
int fout = 0; /* VFS flags returned by xOpen() */
rc = sqlite3OsOpen(pVfs, pPager->zFilename, pPager->fd, vfsFlags, &fout);
readOnly = (fout&SQLITE_OPEN_READONLY);
/* If the file was successfully opened for read/write access,
** choose a default page size in case we have to create the
** database file. The default page size is the maximum of:
**
** + SQLITE_DEFAULT_PAGE_SIZE,
** + The value returned by sqlite3OsSectorSize()
** + The largest page size that can be written atomically.
*/
if( rc==SQLITE_OK && !readOnly ){
setSectorSize(pPager);
assert(SQLITE_DEFAULT_PAGE_SIZE<=SQLITE_MAX_DEFAULT_PAGE_SIZE);
if( szPageDflt<pPager->sectorSize ){
if( pPager->sectorSize>SQLITE_MAX_DEFAULT_PAGE_SIZE ){
szPageDflt = SQLITE_MAX_DEFAULT_PAGE_SIZE;
}else{
szPageDflt = (u16)pPager->sectorSize;
}
}
#ifdef SQLITE_ENABLE_ATOMIC_WRITE
{
int iDc = sqlite3OsDeviceCharacteristics(pPager->fd);
int ii;
assert(SQLITE_IOCAP_ATOMIC512==(512>>8));
assert(SQLITE_IOCAP_ATOMIC64K==(65536>>8));
assert(SQLITE_MAX_DEFAULT_PAGE_SIZE<=65536);
for(ii=szPageDflt; ii<=SQLITE_MAX_DEFAULT_PAGE_SIZE; ii=ii*2){
if( iDc&(SQLITE_IOCAP_ATOMIC|(ii>>8)) ){
szPageDflt = ii;
}
}
}
#endif
}
}else{
/* If a temporary file is requested, it is not opened immediately.
** In this case we accept the default page size and delay actually
** opening the file until the first call to OsWrite().
**
** This branch is also run for an in-memory database. An in-memory
** database is the same as a temp-file that is never written out to
** disk and uses an in-memory rollback journal.
*/
tempFile = 1;
pPager->state = PAGER_EXCLUSIVE;
}
/* The following call to PagerSetPagesize() serves to set the value of
** Pager.pageSize and to allocate the Pager.pTmpSpace buffer.
*/
if( rc==SQLITE_OK ){
assert( pPager->memDb==0 );
rc = sqlite3PagerSetPagesize(pPager, &szPageDflt);
testcase( rc!=SQLITE_OK );
}
/* If an error occurred in either of the blocks above, free the
** Pager structure and close the file.
*/
if( rc!=SQLITE_OK ){
assert( !pPager->pTmpSpace );
sqlite3OsClose(pPager->fd);
sqlite3_free(pPager);
return rc;
}
/* Initialize the PCache object. */
nExtra = ROUND8(nExtra);
sqlite3PcacheOpen(szPageDflt, nExtra, !memDb,
!memDb?pagerStress:0, (void *)pPager, pPager->pPCache);
PAGERTRACE(("OPEN %d %s\n", FILEHANDLEID(pPager->fd), pPager->zFilename));
IOTRACE(("OPEN %p %s\n", pPager, pPager->zFilename))
pPager->useJournal = (u8)useJournal;
pPager->noReadlock = (noReadlock && readOnly) ?1:0;
/* pPager->stmtOpen = 0; */
/* pPager->stmtInUse = 0; */
/* pPager->nRef = 0; */
pPager->dbSizeValid = (u8)memDb;
/* pPager->stmtSize = 0; */
/* pPager->stmtJSize = 0; */
/* pPager->nPage = 0; */
pPager->mxPgno = SQLITE_MAX_PAGE_COUNT;
/* pPager->state = PAGER_UNLOCK; */
assert( pPager->state == (tempFile ? PAGER_EXCLUSIVE : PAGER_UNLOCK) );
/* pPager->errMask = 0; */
pPager->tempFile = (u8)tempFile;
assert( tempFile==PAGER_LOCKINGMODE_NORMAL
|| tempFile==PAGER_LOCKINGMODE_EXCLUSIVE );
assert( PAGER_LOCKINGMODE_EXCLUSIVE==1 );
pPager->exclusiveMode = (u8)tempFile;
pPager->changeCountDone = pPager->tempFile;
pPager->memDb = (u8)memDb;
pPager->readOnly = (u8)readOnly;
/* pPager->needSync = 0; */
pPager->noSync = (pPager->tempFile || !useJournal) ?1:0;
pPager->fullSync = pPager->noSync ?0:1;
pPager->sync_flags = SQLITE_SYNC_NORMAL;
/* pPager->pFirst = 0; */
/* pPager->pFirstSynced = 0; */
/* pPager->pLast = 0; */
pPager->nExtra = nExtra;
pPager->journalSizeLimit = SQLITE_DEFAULT_JOURNAL_SIZE_LIMIT;
assert( isOpen(pPager->fd) || tempFile );
setSectorSize(pPager);
if( memDb ){
pPager->journalMode = PAGER_JOURNALMODE_MEMORY;
}
/* pPager->xBusyHandler = 0; */
/* pPager->pBusyHandlerArg = 0; */
/* memset(pPager->aHash, 0, sizeof(pPager->aHash)); */
*ppPager = pPager;
return SQLITE_OK;
}
/*
** This function is called after transitioning from PAGER_UNLOCK to
** PAGER_SHARED state. It tests if there is a hot journal present in
** the file-system for the given pager. A hot journal is one that
** needs to be played back. According to this function, a hot-journal
** file exists if the following criteria are met:
**
** * The journal file exists in the file system, and
** * No process holds a RESERVED or greater lock on the database file, and
** * The database file itself is greater than 0 bytes in size, and
** * The first byte of the journal file exists and is not 0x00.
**
** If the current size of the database file is 0 but a journal file
** exists, that is probably an old journal left over from a prior
** database with the same name. In this case the journal file is
** just deleted using OsDelete, *pExists is set to 0 and SQLITE_OK
** is returned.
**
** This routine does not check if there is a master journal filename
** at the end of the file. If there is, and that master journal file
** does not exist, then the journal file is not really hot. In this
** case this routine will return a false-positive. The pager_playback()
** routine will discover that the journal file is not really hot and
** will not roll it back.
**
** If a hot-journal file is found to exist, *pExists is set to 1 and
** SQLITE_OK returned. If no hot-journal file is present, *pExists is
** set to 0 and SQLITE_OK returned. If an IO error occurs while trying
** to determine whether or not a hot-journal file exists, the IO error
** code is returned and the value of *pExists is undefined.
*/
static int hasHotJournal(Pager *pPager, int *pExists){
sqlite3_vfs * const pVfs = pPager->pVfs;
int rc; /* Return code */
int exists; /* True if a journal file is present */
assert( pPager!=0 );
assert( pPager->useJournal );
assert( isOpen(pPager->fd) );
assert( !isOpen(pPager->jfd) );
*pExists = 0;
rc = sqlite3OsAccess(pVfs, pPager->zJournal, SQLITE_ACCESS_EXISTS, &exists);
if( rc==SQLITE_OK && exists ){
int locked; /* True if some process holds a RESERVED lock */
rc = sqlite3OsCheckReservedLock(pPager->fd, &locked);
if( rc==SQLITE_OK && !locked ){
int nPage;
/* Check the size of the database file. If it consists of 0 pages,
** then delete the journal file. See the header comment above for
** the reasoning here.
*/
rc = sqlite3PagerPagecount(pPager, &nPage);
if( rc==SQLITE_OK ){
if( nPage==0 ){
rc = sqlite3OsDelete(pVfs, pPager->zJournal, 0);
}else{
/* The journal file exists and no other connection has a reserved
** or greater lock on the database file. Now check that there is
** at least one non-zero bytes at the start of the journal file.
** If there is, then we consider this journal to be hot. If not,
** it can be ignored.
*/
int f = SQLITE_OPEN_READONLY|SQLITE_OPEN_MAIN_JOURNAL;
rc = sqlite3OsOpen(pVfs, pPager->zJournal, pPager->jfd, f, &f);
if( rc==SQLITE_OK ){
u8 first = 0;
rc = sqlite3OsRead(pPager->jfd, (void *)&first, 1, 0);
if( rc==SQLITE_IOERR_SHORT_READ ){
rc = SQLITE_OK;
}
sqlite3OsClose(pPager->jfd);
*pExists = (first!=0);
}
}
}
}
}
return rc;
}
/*
** Read the content for page pPg out of the database file and into
** pPg->pData. A shared lock or greater must be held on the database
** file before this function is called.
**
** If page 1 is read, then the value of Pager.dbFileVers[] is set to
** the value read from the database file.
**
** If an IO error occurs, then the IO error is returned to the caller.
** Otherwise, SQLITE_OK is returned.
*/
static int readDbPage(PgHdr *pPg){
Pager *pPager = pPg->pPager; /* Pager object associated with page pPg */
Pgno pgno = pPg->pgno; /* Page number to read */
int rc; /* Return code */
i64 iOffset; /* Byte offset of file to read from */
assert( pPager->state>=PAGER_SHARED && !MEMDB );
if( !isOpen(pPager->fd) ){
assert( pPager->tempFile );
memset(pPg->pData, 0, pPager->pageSize);
return SQLITE_OK;
}
iOffset = (pgno-1)*(i64)pPager->pageSize;
rc = sqlite3OsRead(pPager->fd, pPg->pData, pPager->pageSize, iOffset);
if( rc==SQLITE_IOERR_SHORT_READ ){
rc = SQLITE_OK;
}
if( pgno==1 ){
u8 *dbFileVers = &((u8*)pPg->pData)[24];
memcpy(&pPager->dbFileVers, dbFileVers, sizeof(pPager->dbFileVers));
}
CODEC1(pPager, pPg->pData, pgno, 3);
PAGER_INCR(sqlite3_pager_readdb_count);
PAGER_INCR(pPager->nRead);
IOTRACE(("PGIN %p %d\n", pPager, pgno));
PAGERTRACE(("FETCH %d page %d hash(%08x)\n",
PAGERID(pPager), pgno, pager_pagehash(pPg)));
return rc;
}
/*
** This function is called whenever the upper layer requests a database
** page is requested, before the cache is checked for a suitable page
** or any data is read from the database. It performs the following
** two functions:
**
** 1) If the pager is currently in PAGER_UNLOCK state (no lock held
** on the database file), then an attempt is made to obtain a
** SHARED lock on the database file. Immediately after obtaining
** the SHARED lock, the file-system is checked for a hot-journal,
** which is played back if present. Following any hot-journal
** rollback, the contents of the cache are validated by checking
** the 'change-counter' field of the database file header and
** discarded if they are found to be invalid.
**
** 2) If the pager is running in exclusive-mode, and there are currently
** no outstanding references to any pages, and is in the error state,
** then an attempt is made to clear the error state by discarding
** the contents of the page cache and rolling back any open journal
** file.
**
** If the operation described by (2) above is not attempted, and if the
** pager is in an error state other than SQLITE_FULL when this is called,
** the error state error code is returned. It is permitted to read the
** database when in SQLITE_FULL error state.
**
** Otherwise, if everything is successful, SQLITE_OK is returned. If an
** IO error occurs while locking the database, checking for a hot-journal
** file or rolling back a journal file, the IO error code is returned.
*/
static int pagerSharedLock(Pager *pPager){
int rc = SQLITE_OK; /* Return code */
int isErrorReset = 0; /* True if recovering from error state */
/* If this database is opened for exclusive access, has no outstanding
** page references and is in an error-state, this is a chance to clear
** the error. Discard the contents of the pager-cache and treat any
** open journal file as a hot-journal.
*/
if( !MEMDB && pPager->exclusiveMode
&& sqlite3PcacheRefCount(pPager->pPCache)==0 && pPager->errCode
){
if( isOpen(pPager->jfd) ){
isErrorReset = 1;
}
pPager->errCode = SQLITE_OK;
pager_reset(pPager);
}
/* If the pager is still in an error state, do not proceed. The error
** state will be cleared at some point in the future when all page
** references are dropped and the cache can be discarded.
*/
if( pPager->errCode && pPager->errCode!=SQLITE_FULL ){
return pPager->errCode;
}
if( pPager->state==PAGER_UNLOCK || isErrorReset ){
sqlite3_vfs * const pVfs = pPager->pVfs;
int isHotJournal = 0;
assert( !MEMDB );
assert( sqlite3PcacheRefCount(pPager->pPCache)==0 );
if( !pPager->noReadlock ){
rc = pager_wait_on_lock(pPager, SHARED_LOCK);
if( rc!=SQLITE_OK ){
assert( pPager->state==PAGER_UNLOCK );
return pager_error(pPager, rc);
}
}else if( pPager->state==PAGER_UNLOCK ){
pPager->state = PAGER_SHARED;
}
assert( pPager->state>=SHARED_LOCK );
/* If a journal file exists, and there is no RESERVED lock on the
** database file, then it either needs to be played back or deleted.
*/
if( !isErrorReset ){
rc = hasHotJournal(pPager, &isHotJournal);
if( rc!=SQLITE_OK ){
goto failed;
}
}
if( isErrorReset || isHotJournal ){
/* Get an EXCLUSIVE lock on the database file. At this point it is
** important that a RESERVED lock is not obtained on the way to the
** EXCLUSIVE lock. If it were, another process might open the
** database file, detect the RESERVED lock, and conclude that the
** database is safe to read while this process is still rolling the
** hot-journal back.
**
** Because the intermediate RESERVED lock is not requested, any
** other process attempting to access the database file will get to
** this point in the code and fail to obtain its own EXCLUSIVE lock
** on the database file.
*/
if( pPager->state<EXCLUSIVE_LOCK ){
rc = sqlite3OsLock(pPager->fd, EXCLUSIVE_LOCK);
if( rc!=SQLITE_OK ){
rc = pager_error(pPager, rc);
goto failed;
}
pPager->state = PAGER_EXCLUSIVE;
}
/* Open the journal for read/write access. This is because in
** exclusive-access mode the file descriptor will be kept open and
** possibly used for a transaction later on. On some systems, the
** OsTruncate() call used in exclusive-access mode also requires
** a read/write file handle.
*/
if( !isOpen(pPager->jfd) ){
int res;
rc = sqlite3OsAccess(pVfs,pPager->zJournal,SQLITE_ACCESS_EXISTS,&res);
if( rc==SQLITE_OK ){
if( res ){
int fout = 0;
int f = SQLITE_OPEN_READWRITE|SQLITE_OPEN_MAIN_JOURNAL;
assert( !pPager->tempFile );
rc = sqlite3OsOpen(pVfs, pPager->zJournal, pPager->jfd, f, &fout);
assert( rc!=SQLITE_OK || isOpen(pPager->jfd) );
if( rc==SQLITE_OK && fout&SQLITE_OPEN_READONLY ){
rc = SQLITE_CANTOPEN;
sqlite3OsClose(pPager->jfd);
}
}else{
/* If the journal does not exist, that means some other process
** has already rolled it back */
rc = SQLITE_BUSY;
}
}
}
if( rc!=SQLITE_OK ){
goto failed;
}
/* TODO: Why are these cleared here? Is it necessary? */
pPager->journalStarted = 0;
pPager->journalOff = 0;
pPager->setMaster = 0;
pPager->journalHdr = 0;
/* Playback and delete the journal. Drop the database write
** lock and reacquire the read lock. Purge the cache before
** playing back the hot-journal so that we don't end up with
** an inconsistent cache.
*/
rc = pager_playback(pPager, 1);
if( rc!=SQLITE_OK ){
rc = pager_error(pPager, rc);
goto failed;
}
assert( (pPager->state==PAGER_SHARED)
|| (pPager->exclusiveMode && pPager->state>PAGER_SHARED)
);
}
if( pPager->pBackup || sqlite3PcachePagecount(pPager->pPCache)>0 ){
/* The shared-lock has just been acquired on the database file
** and there are already pages in the cache (from a previous
** read or write transaction). Check to see if the database
** has been modified. If the database has changed, flush the
** cache.
**
** Database changes is detected by looking at 15 bytes beginning
** at offset 24 into the file. The first 4 of these 16 bytes are
** a 32-bit counter that is incremented with each change. The
** other bytes change randomly with each file change when
** a codec is in use.
**
** There is a vanishingly small chance that a change will not be
** detected. The chance of an undetected change is so small that
** it can be neglected.
*/
char dbFileVers[sizeof(pPager->dbFileVers)];
sqlite3PagerPagecount(pPager, 0);
if( pPager->errCode ){
rc = pPager->errCode;
goto failed;
}
assert( pPager->dbSizeValid );
if( pPager->dbSize>0 ){
IOTRACE(("CKVERS %p %d\n", pPager, sizeof(dbFileVers)));
rc = sqlite3OsRead(pPager->fd, &dbFileVers, sizeof(dbFileVers), 24);
if( rc!=SQLITE_OK ){
goto failed;
}
}else{
memset(dbFileVers, 0, sizeof(dbFileVers));
}
if( memcmp(pPager->dbFileVers, dbFileVers, sizeof(dbFileVers))!=0 ){
pager_reset(pPager);
}
}
assert( pPager->exclusiveMode || pPager->state==PAGER_SHARED );
}
failed:
if( rc!=SQLITE_OK ){
/* pager_unlock() is a no-op for exclusive mode and in-memory databases. */
pager_unlock(pPager);
}
return rc;
}
/*
** If the reference count has reached zero, rollback any active
** transaction and unlock the pager.
**
** Except, in locking_mode=EXCLUSIVE when there is nothing to in
** the rollback journal, the unlock is not performed and there is
** nothing to rollback, so this routine is a no-op.
*/
static void pagerUnlockIfUnused(Pager *pPager){
if( (sqlite3PcacheRefCount(pPager->pPCache)==0)
&& (!pPager->exclusiveMode || pPager->journalOff>0)
){
pagerUnlockAndRollback(pPager);
}
}
/*
** Drop a page from the cache using sqlite3PcacheDrop().
**
** If this means there are now no pages with references to them, a rollback
** occurs and the lock on the database is removed.
*/
static void pagerDropPage(DbPage *pPg){
Pager *pPager = pPg->pPager;
sqlite3PcacheDrop(pPg);
pagerUnlockIfUnused(pPager);
}
/*
** Acquire a reference to page number pgno in pager pPager (a page
** reference has type DbPage*). If the requested reference is
** successfully obtained, it is copied to *ppPage and SQLITE_OK returned.
**
** This function calls pagerSharedLock() to obtain a SHARED lock on
** the database file if such a lock or greater is not already held.
** This may cause hot-journal rollback or a cache purge. See comments
** above function pagerSharedLock() for details.
**
** If the requested page is already in the cache, it is returned.
** Otherwise, a new page object is allocated and populated with data
** read from the database file. In some cases, the pcache module may
** choose not to allocate a new page object and may reuse an existing
** object with no outstanding references.
**
** The extra data appended to a page is always initialized to zeros the
** first time a page is loaded into memory. If the page requested is
** already in the cache when this function is called, then the extra
** data is left as it was when the page object was last used.
**
** If the database image is smaller than the requested page or if a
** non-zero value is passed as the noContent parameter and the
** requested page is not already stored in the cache, then no
** actual disk read occurs. In this case the memory image of the
** page is initialized to all zeros.
**
** If noContent is true, it means that we do not care about the contents
** of the page. This occurs in two seperate scenarios:
**
** a) When reading a free-list leaf page from the database, and
**
** b) When a savepoint is being rolled back and we need to load
** a new page into the cache to populate with the data read
** from the savepoint journal.
**
** If noContent is true, then the data returned is zeroed instead of
** being read from the database. Additionally, the bits corresponding
** to pgno in Pager.pInJournal (bitvec of pages already written to the
** journal file) and the PagerSavepoint.pInSavepoint bitvecs of any open
** savepoints are set. This means if the page is made writable at any
** point in the future, using a call to sqlite3PagerWrite(), its contents
** will not be journaled. This saves IO.
**
** The acquisition might fail for several reasons. In all cases,
** an appropriate error code is returned and *ppPage is set to NULL.
**
** See also sqlite3PagerLookup(). Both this routine and Lookup() attempt
** to find a page in the in-memory cache first. If the page is not already
** in memory, this routine goes to disk to read it in whereas Lookup()
** just returns 0. This routine acquires a read-lock the first time it
** has to go to disk, and could also playback an old journal if necessary.
** Since Lookup() never goes to disk, it never has to deal with locks
** or journal files.
*/
int sqlite3PagerAcquire(
Pager *pPager, /* The pager open on the database file */
Pgno pgno, /* Page number to fetch */
DbPage **ppPage, /* Write a pointer to the page here */
int noContent /* Do not bother reading content from disk if true */
){
PgHdr *pPg = 0;
int rc;
assert( assert_pager_state(pPager) );
assert( pPager->state==PAGER_UNLOCK
|| sqlite3PcacheRefCount(pPager->pPCache)>0
|| pgno==1
);
/* The maximum page number is 2^31. Return SQLITE_CORRUPT if a page
** number greater than this, or zero, is requested.
*/
if( pgno>PAGER_MAX_PGNO || pgno==0 || pgno==PAGER_MJ_PGNO(pPager) ){
return SQLITE_CORRUPT_BKPT;
}
/* Make sure we have not hit any critical errors.
*/
assert( pPager!=0 );
*ppPage = 0;
/* If this is the first page accessed, then get a SHARED lock
** on the database file. pagerSharedLock() is a no-op if
** a database lock is already held.
*/
rc = pagerSharedLock(pPager);
if( rc!=SQLITE_OK ){
return rc;
}
assert( pPager->state!=PAGER_UNLOCK );
rc = sqlite3PcacheFetch(pPager->pPCache, pgno, 1, &pPg);
if( rc!=SQLITE_OK ){
return rc;
}
assert( pPg->pgno==pgno );
assert( pPg->pPager==pPager || pPg->pPager==0 );
if( pPg->pPager==0 ){
/* The pager cache has created a new page. Its content needs to
** be initialized.
*/
int nMax;
PAGER_INCR(pPager->nMiss);
pPg->pPager = pPager;
rc = sqlite3PagerPagecount(pPager, &nMax);
if( rc!=SQLITE_OK ){
sqlite3PagerUnref(pPg);
return rc;
}
if( nMax<(int)pgno || MEMDB || noContent ){
if( pgno>pPager->mxPgno ){
sqlite3PagerUnref(pPg);
return SQLITE_FULL;
}
if( noContent ){
/* Failure to set the bits in the InJournal bit-vectors is benign.
** It merely means that we might do some extra work to journal a
** page that does not need to be journaled. Nevertheless, be sure
** to test the case where a malloc error occurs while trying to set
** a bit in a bit vector.
*/
sqlite3BeginBenignMalloc();
if( pgno<=pPager->dbOrigSize ){
TESTONLY( rc = ) sqlite3BitvecSet(pPager->pInJournal, pgno);
testcase( rc==SQLITE_NOMEM );
}
TESTONLY( rc = ) addToSavepointBitvecs(pPager, pgno);
testcase( rc==SQLITE_NOMEM );
sqlite3EndBenignMalloc();
}else{
memset(pPg->pData, 0, pPager->pageSize);
}
IOTRACE(("ZERO %p %d\n", pPager, pgno));
}else{
assert( pPg->pPager==pPager );
rc = readDbPage(pPg);
if( rc!=SQLITE_OK ){
pagerDropPage(pPg);
return rc;
}
}
#ifdef SQLITE_CHECK_PAGES
pPg->pageHash = pager_pagehash(pPg);
#endif
}else{
/* The requested page is in the page cache. */
PAGER_INCR(pPager->nHit);
}
*ppPage = pPg;
return SQLITE_OK;
}
/*
** Acquire a page if it is already in the in-memory cache. Do
** not read the page from disk. Return a pointer to the page,
** or 0 if the page is not in cache. Also, return 0 if the
** pager is in PAGER_UNLOCK state when this function is called,
** or if the pager is in an error state other than SQLITE_FULL.
**
** See also sqlite3PagerGet(). The difference between this routine
** and sqlite3PagerGet() is that _get() will go to the disk and read
** in the page if the page is not already in cache. This routine
** returns NULL if the page is not in cache or if a disk I/O error
** has ever happened.
*/
DbPage *sqlite3PagerLookup(Pager *pPager, Pgno pgno){
PgHdr *pPg = 0;
assert( pPager!=0 );
assert( pgno!=0 );
if( (pPager->state!=PAGER_UNLOCK)
&& (pPager->errCode==SQLITE_OK || pPager->errCode==SQLITE_FULL)
){
sqlite3PcacheFetch(pPager->pPCache, pgno, 0, &pPg);
}
return pPg;
}
/*
** Release a page reference.
**
** If the number of references to the page drop to zero, then the
** page is added to the LRU list. When all references to all pages
** are released, a rollback occurs and the lock on the database is
** removed.
*/
void sqlite3PagerUnref(DbPage *pPg){
if( pPg ){
Pager *pPager = pPg->pPager;
sqlite3PcacheRelease(pPg);
pagerUnlockIfUnused(pPager);
}
}
/*
** If the main journal file has already been opened, ensure that the
** sub-journal file is open too. If the main journal is not open,
** this function is a no-op.
**
** SQLITE_OK is returned if everything goes according to plan.
** An SQLITE_IOERR_XXX error code is returned if a call to
** sqlite3OsOpen() fails.
*/
static int openSubJournal(Pager *pPager){
int rc = SQLITE_OK;
if( isOpen(pPager->jfd) && !isOpen(pPager->sjfd) ){
if( pPager->journalMode==PAGER_JOURNALMODE_MEMORY || pPager->subjInMemory ){
sqlite3MemJournalOpen(pPager->sjfd);
}else{
rc = pagerOpentemp(pPager, pPager->sjfd, SQLITE_OPEN_SUBJOURNAL);
}
}
return rc;
}
/*
** This function is called at the start of every write transaction.
** There must already be a RESERVED or EXCLUSIVE lock on the database
** file when this routine is called.
**
** Open the journal file for pager pPager and write a journal header
** to the start of it. If there are active savepoints, open the sub-journal
** as well. This function is only used when the journal file is being
** opened to write a rollback log for a transaction. It is not used
** when opening a hot journal file to roll it back.
**
** If the journal file is already open (as it may be in exclusive mode),
** then this function just writes a journal header to the start of the
** already open file.
**
** Whether or not the journal file is opened by this function, the
** Pager.pInJournal bitvec structure is allocated.
**
** Return SQLITE_OK if everything is successful. Otherwise, return
** SQLITE_NOMEM if the attempt to allocate Pager.pInJournal fails, or
** an IO error code if opening or writing the journal file fails.
*/
static int pager_open_journal(Pager *pPager){
int rc = SQLITE_OK; /* Return code */
sqlite3_vfs * const pVfs = pPager->pVfs; /* Local cache of vfs pointer */
assert( pPager->state>=PAGER_RESERVED );
assert( pPager->useJournal );
assert( pPager->pInJournal==0 );
/* If already in the error state, this function is a no-op. */
if( pPager->errCode ){
return pPager->errCode;
}
/* TODO: Is it really possible to get here with dbSizeValid==0? If not,
** the call to PagerPagecount() can be removed.
*/
testcase( pPager->dbSizeValid==0 );
sqlite3PagerPagecount(pPager, 0);
pPager->pInJournal = sqlite3BitvecCreate(pPager->dbSize);
if( pPager->pInJournal==0 ){
return SQLITE_NOMEM;
}
/* Open the journal file if it is not already open. */
if( !isOpen(pPager->jfd) ){
if( pPager->journalMode==PAGER_JOURNALMODE_MEMORY ){
sqlite3MemJournalOpen(pPager->jfd);
}else{
const int flags = /* VFS flags to open journal file */
SQLITE_OPEN_READWRITE|SQLITE_OPEN_CREATE|
(pPager->tempFile ?
(SQLITE_OPEN_DELETEONCLOSE|SQLITE_OPEN_TEMP_JOURNAL):
(SQLITE_OPEN_MAIN_JOURNAL)
);
#ifdef SQLITE_ENABLE_ATOMIC_WRITE
rc = sqlite3JournalOpen(
pVfs, pPager->zJournal, pPager->jfd, flags, jrnlBufferSize(pPager)
);
#else
rc = sqlite3OsOpen(pVfs, pPager->zJournal, pPager->jfd, flags, 0);
#endif
}
assert( rc!=SQLITE_OK || isOpen(pPager->jfd) );
}
/* Write the first journal header to the journal file and open
** the sub-journal if necessary.
*/
if( rc==SQLITE_OK ){
/* TODO: Check if all of these are really required. */
pPager->dbOrigSize = pPager->dbSize;
pPager->journalStarted = 0;
pPager->needSync = 0;
pPager->nRec = 0;
pPager->journalOff = 0;
pPager->setMaster = 0;
pPager->journalHdr = 0;
rc = writeJournalHdr(pPager);
}
if( rc==SQLITE_OK && pPager->nSavepoint ){
rc = openSubJournal(pPager);
}
if( rc!=SQLITE_OK ){
sqlite3BitvecDestroy(pPager->pInJournal);
pPager->pInJournal = 0;
}
return rc;
}
/*
** Begin a write-transaction on the specified pager object. If a
** write-transaction has already been opened, this function is a no-op.
**
** If the exFlag argument is false, then acquire at least a RESERVED
** lock on the database file. If exFlag is true, then acquire at least
** an EXCLUSIVE lock. If such a lock is already held, no locking
** functions need be called.
**
** If this is not a temporary or in-memory file and, the journal file is
** opened if it has not been already. For a temporary file, the opening
** of the journal file is deferred until there is an actual need to
** write to the journal. TODO: Why handle temporary files differently?
**
** If the journal file is opened (or if it is already open), then a
** journal-header is written to the start of it.
**
** If the subjInMemory argument is non-zero, then any sub-journal opened
** within this transaction will be opened as an in-memory file. This
** has no effect if the sub-journal is already opened (as it may be when
** running in exclusive mode) or if the transaction does not require a
** sub-journal. If the subjInMemory argument is zero, then any required
** sub-journal is implemented in-memory if pPager is an in-memory database,
** or using a temporary file otherwise.
*/
int sqlite3PagerBegin(Pager *pPager, int exFlag, int subjInMemory){
int rc = SQLITE_OK;
assert( pPager->state!=PAGER_UNLOCK );
pPager->subjInMemory = (u8)subjInMemory;
if( pPager->state==PAGER_SHARED ){
assert( pPager->pInJournal==0 );
assert( !MEMDB && !pPager->tempFile );
/* Obtain a RESERVED lock on the database file. If the exFlag parameter
** is true, then immediately upgrade this to an EXCLUSIVE lock. The
** busy-handler callback can be used when upgrading to the EXCLUSIVE
** lock, but not when obtaining the RESERVED lock.
*/
rc = sqlite3OsLock(pPager->fd, RESERVED_LOCK);
if( rc==SQLITE_OK ){
pPager->state = PAGER_RESERVED;
if( exFlag ){
rc = pager_wait_on_lock(pPager, EXCLUSIVE_LOCK);
}
}
/* If the required locks were successfully obtained, open the journal
** file and write the first journal-header to it.
*/
if( rc==SQLITE_OK && pPager->useJournal
&& pPager->journalMode!=PAGER_JOURNALMODE_OFF
){
rc = pager_open_journal(pPager);
}
}else if( isOpen(pPager->jfd) && pPager->journalOff==0 ){
/* This happens when the pager was in exclusive-access mode the last
** time a (read or write) transaction was successfully concluded
** by this connection. Instead of deleting the journal file it was
** kept open and either was truncated to 0 bytes or its header was
** overwritten with zeros.
*/
assert( pPager->nRec==0 );
assert( pPager->dbOrigSize==0 );
assert( pPager->pInJournal==0 );
rc = pager_open_journal(pPager);
}
PAGERTRACE(("TRANSACTION %d\n", PAGERID(pPager)));
assert( !isOpen(pPager->jfd) || pPager->journalOff>0 || rc!=SQLITE_OK );
return rc;
}
/*
** Mark a single data page as writeable. The page is written into the
** main journal or sub-journal as required. If the page is written into
** one of the journals, the corresponding bit is set in the
** Pager.pInJournal bitvec and the PagerSavepoint.pInSavepoint bitvecs
** of any open savepoints as appropriate.
*/
static int pager_write(PgHdr *pPg){
void *pData = pPg->pData;
Pager *pPager = pPg->pPager;
int rc = SQLITE_OK;
/* Check for errors
*/
if( pPager->errCode ){
return pPager->errCode;
}
if( pPager->readOnly ){
return SQLITE_PERM;
}
assert( !pPager->setMaster );
CHECK_PAGE(pPg);
/* Mark the page as dirty. If the page has already been written
** to the journal then we can return right away.
*/
sqlite3PcacheMakeDirty(pPg);
if( pageInJournal(pPg) && !subjRequiresPage(pPg) ){
pPager->dbModified = 1;
}else{
/* If we get this far, it means that the page needs to be
** written to the transaction journal or the ckeckpoint journal
** or both.
**
** First check to see that the transaction journal exists and
** create it if it does not.
*/
assert( pPager->state!=PAGER_UNLOCK );
rc = sqlite3PagerBegin(pPager, 0, pPager->subjInMemory);
if( rc!=SQLITE_OK ){
return rc;
}
assert( pPager->state>=PAGER_RESERVED );
if( !isOpen(pPager->jfd) && pPager->useJournal
&& pPager->journalMode!=PAGER_JOURNALMODE_OFF ){
rc = pager_open_journal(pPager);
if( rc!=SQLITE_OK ) return rc;
}
pPager->dbModified = 1;
/* The transaction journal now exists and we have a RESERVED or an
** EXCLUSIVE lock on the main database file. Write the current page to
** the transaction journal if it is not there already.
*/
if( !pageInJournal(pPg) && isOpen(pPager->jfd) ){
if( pPg->pgno<=pPager->dbOrigSize ){
u32 cksum;
char *pData2;
/* We should never write to the journal file the page that
** contains the database locks. The following assert verifies
** that we do not. */
assert( pPg->pgno!=PAGER_MJ_PGNO(pPager) );
pData2 = CODEC2(pPager, pData, pPg->pgno, 7);
cksum = pager_cksum(pPager, (u8*)pData2);
rc = write32bits(pPager->jfd, pPager->journalOff, pPg->pgno);
if( rc==SQLITE_OK ){
rc = sqlite3OsWrite(pPager->jfd, pData2, pPager->pageSize,
pPager->journalOff + 4);
pPager->journalOff += pPager->pageSize+4;
}
if( rc==SQLITE_OK ){
rc = write32bits(pPager->jfd, pPager->journalOff, cksum);
pPager->journalOff += 4;
}
IOTRACE(("JOUT %p %d %lld %d\n", pPager, pPg->pgno,
pPager->journalOff, pPager->pageSize));
PAGER_INCR(sqlite3_pager_writej_count);
PAGERTRACE(("JOURNAL %d page %d needSync=%d hash(%08x)\n",
PAGERID(pPager), pPg->pgno,
((pPg->flags&PGHDR_NEED_SYNC)?1:0), pager_pagehash(pPg)));
/* Even if an IO or diskfull error occurred while journalling the
** page in the block above, set the need-sync flag for the page.
** Otherwise, when the transaction is rolled back, the logic in
** playback_one_page() will think that the page needs to be restored
** in the database file. And if an IO error occurs while doing so,
** then corruption may follow.
*/
if( !pPager->noSync ){
pPg->flags |= PGHDR_NEED_SYNC;
pPager->needSync = 1;
}
/* An error has occurred writing to the journal file. The
** transaction will be rolled back by the layer above.
*/
if( rc!=SQLITE_OK ){
return rc;
}
pPager->nRec++;
assert( pPager->pInJournal!=0 );
rc = sqlite3BitvecSet(pPager->pInJournal, pPg->pgno);
testcase( rc==SQLITE_NOMEM );
assert( rc==SQLITE_OK || rc==SQLITE_NOMEM );
rc |= addToSavepointBitvecs(pPager, pPg->pgno);
if( rc!=SQLITE_OK ){
assert( rc==SQLITE_NOMEM );
return rc;
}
}else{
if( !pPager->journalStarted && !pPager->noSync ){
pPg->flags |= PGHDR_NEED_SYNC;
pPager->needSync = 1;
}
PAGERTRACE(("APPEND %d page %d needSync=%d\n",
PAGERID(pPager), pPg->pgno,
((pPg->flags&PGHDR_NEED_SYNC)?1:0)));
}
}
/* If the statement journal is open and the page is not in it,
** then write the current page to the statement journal. Note that
** the statement journal format differs from the standard journal format
** in that it omits the checksums and the header.
*/
if( subjRequiresPage(pPg) ){
rc = subjournalPage(pPg);
}
}
/* Update the database size and return.
*/
assert( pPager->state>=PAGER_SHARED );
if( pPager->dbSize<pPg->pgno ){
pPager->dbSize = pPg->pgno;
}
return rc;
}
/*
** Mark a data page as writeable. This routine must be called before
** making changes to a page. The caller must check the return value
** of this function and be careful not to change any page data unless
** this routine returns SQLITE_OK.
**
** The difference between this function and pager_write() is that this
** function also deals with the special case where 2 or more pages
** fit on a single disk sector. In this case all co-resident pages
** must have been written to the journal file before returning.
**
** If an error occurs, SQLITE_NOMEM or an IO error code is returned
** as appropriate. Otherwise, SQLITE_OK.
*/
int sqlite3PagerWrite(DbPage *pDbPage){
int rc = SQLITE_OK;
PgHdr *pPg = pDbPage;
Pager *pPager = pPg->pPager;
Pgno nPagePerSector = (pPager->sectorSize/pPager->pageSize);
if( nPagePerSector>1 ){
Pgno nPageCount; /* Total number of pages in database file */
Pgno pg1; /* First page of the sector pPg is located on. */
int nPage; /* Number of pages starting at pg1 to journal */
int ii; /* Loop counter */
int needSync = 0; /* True if any page has PGHDR_NEED_SYNC */
/* Set the doNotSync flag to 1. This is because we cannot allow a journal
** header to be written between the pages journaled by this function.
*/
assert( !MEMDB );
assert( pPager->doNotSync==0 );
pPager->doNotSync = 1;
/* This trick assumes that both the page-size and sector-size are
** an integer power of 2. It sets variable pg1 to the identifier
** of the first page of the sector pPg is located on.
*/
pg1 = ((pPg->pgno-1) & ~(nPagePerSector-1)) + 1;
sqlite3PagerPagecount(pPager, (int *)&nPageCount);
if( pPg->pgno>nPageCount ){
nPage = (pPg->pgno - pg1)+1;
}else if( (pg1+nPagePerSector-1)>nPageCount ){
nPage = nPageCount+1-pg1;
}else{
nPage = nPagePerSector;
}
assert(nPage>0);
assert(pg1<=pPg->pgno);
assert((pg1+nPage)>pPg->pgno);
for(ii=0; ii<nPage && rc==SQLITE_OK; ii++){
Pgno pg = pg1+ii;
PgHdr *pPage;
if( pg==pPg->pgno || !sqlite3BitvecTest(pPager->pInJournal, pg) ){
if( pg!=PAGER_MJ_PGNO(pPager) ){
rc = sqlite3PagerGet(pPager, pg, &pPage);
if( rc==SQLITE_OK ){
rc = pager_write(pPage);
if( pPage->flags&PGHDR_NEED_SYNC ){
needSync = 1;
assert(pPager->needSync);
}
sqlite3PagerUnref(pPage);
}
}
}else if( (pPage = pager_lookup(pPager, pg))!=0 ){
if( pPage->flags&PGHDR_NEED_SYNC ){
needSync = 1;
}
sqlite3PagerUnref(pPage);
}
}
/* If the PGHDR_NEED_SYNC flag is set for any of the nPage pages
** starting at pg1, then it needs to be set for all of them. Because
** writing to any of these nPage pages may damage the others, the
** journal file must contain sync()ed copies of all of them
** before any of them can be written out to the database file.
*/
if( needSync ){
assert( !MEMDB && pPager->noSync==0 );
for(ii=0; ii<nPage && needSync; ii++){
PgHdr *pPage = pager_lookup(pPager, pg1+ii);
if( pPage ){
pPage->flags |= PGHDR_NEED_SYNC;
sqlite3PagerUnref(pPage);
}
}
assert(pPager->needSync);
}
assert( pPager->doNotSync==1 );
pPager->doNotSync = 0;
}else{
rc = pager_write(pDbPage);
}
return rc;
}
/*
** Return TRUE if the page given in the argument was previously passed
** to sqlite3PagerWrite(). In other words, return TRUE if it is ok
** to change the content of the page.
*/
#ifndef NDEBUG
int sqlite3PagerIswriteable(DbPage *pPg){
return pPg->flags&PGHDR_DIRTY;
}
#endif
/*
** A call to this routine tells the pager that it is not necessary to
** write the information on page pPg back to the disk, even though
** that page might be marked as dirty. This happens, for example, when
** the page has been added as a leaf of the freelist and so its
** content no longer matters.
**
** The overlying software layer calls this routine when all of the data
** on the given page is unused. The pager marks the page as clean so
** that it does not get written to disk.
**
** Tests show that this optimization can quadruple the speed of large
** DELETE operations.
*/
void sqlite3PagerDontWrite(PgHdr *pPg){
Pager *pPager = pPg->pPager;
if( (pPg->flags&PGHDR_DIRTY) && pPager->nSavepoint==0 ){
PAGERTRACE(("DONT_WRITE page %d of %d\n", pPg->pgno, PAGERID(pPager)));
IOTRACE(("CLEAN %p %d\n", pPager, pPg->pgno))
pPg->flags |= PGHDR_DONT_WRITE;
#ifdef SQLITE_CHECK_PAGES
pPg->pageHash = pager_pagehash(pPg);
#endif
}
}
/*
** This routine is called to increment the value of the database file
** change-counter, stored as a 4-byte big-endian integer starting at
** byte offset 24 of the pager file.
**
** If the isDirect flag is zero, then this is done by calling
** sqlite3PagerWrite() on page 1, then modifying the contents of the
** page data. In this case the file will be updated when the current
** transaction is committed.
**
** The isDirect flag may only be non-zero if the library was compiled
** with the SQLITE_ENABLE_ATOMIC_WRITE macro defined. In this case,
** if isDirect is non-zero, then the database file is updated directly
** by writing an updated version of page 1 using a call to the
** sqlite3OsWrite() function.
*/
static int pager_incr_changecounter(Pager *pPager, int isDirectMode){
int rc = SQLITE_OK;
/* Declare and initialize constant integer 'isDirect'. If the
** atomic-write optimization is enabled in this build, then isDirect
** is initialized to the value passed as the isDirectMode parameter
** to this function. Otherwise, it is always set to zero.
**
** The idea is that if the atomic-write optimization is not
** enabled at compile time, the compiler can omit the tests of
** 'isDirect' below, as well as the block enclosed in the
** "if( isDirect )" condition.
*/
#ifndef SQLITE_ENABLE_ATOMIC_WRITE
const int isDirect = 0;
assert( isDirectMode==0 );
UNUSED_PARAMETER(isDirectMode);
#else
const int isDirect = isDirectMode;
#endif
assert( pPager->state>=PAGER_RESERVED );
if( !pPager->changeCountDone && pPager->dbSize>0 ){
PgHdr *pPgHdr; /* Reference to page 1 */
u32 change_counter; /* Initial value of change-counter field */
assert( !pPager->tempFile && isOpen(pPager->fd) );
/* Open page 1 of the file for writing. */
rc = sqlite3PagerGet(pPager, 1, &pPgHdr);
assert( pPgHdr==0 || rc==SQLITE_OK );
/* If page one was fetched successfully, and this function is not
** operating in direct-mode, make page 1 writable.
*/
if( rc==SQLITE_OK && !isDirect ){
rc = sqlite3PagerWrite(pPgHdr);
}
if( rc==SQLITE_OK ){
/* Increment the value just read and write it back to byte 24. */
change_counter = sqlite3Get4byte((u8*)pPager->dbFileVers);
change_counter++;
put32bits(((char*)pPgHdr->pData)+24, change_counter);
/* If running in direct mode, write the contents of page 1 to the file. */
if( isDirect ){
const void *zBuf = pPgHdr->pData;
assert( pPager->dbFileSize>0 );
rc = sqlite3OsWrite(pPager->fd, zBuf, pPager->pageSize, 0);
}
/* If everything worked, set the changeCountDone flag. */
if( rc==SQLITE_OK ){
pPager->changeCountDone = 1;
}
}
/* Release the page reference. */
sqlite3PagerUnref(pPgHdr);
}
return rc;
}
/*
** Sync the pager file to disk. This is a no-op for in-memory files
** or pages with the Pager.noSync flag set.
**
** If successful, or called on a pager for which it is a no-op, this
** function returns SQLITE_OK. Otherwise, an IO error code is returned.
*/
int sqlite3PagerSync(Pager *pPager){
int rc; /* Return code */
if( MEMDB || pPager->noSync ){
rc = SQLITE_OK;
}else{
rc = sqlite3OsSync(pPager->fd, pPager->sync_flags);
}
return rc;
}
/*
** Sync the database file for the pager pPager. zMaster points to the name
** of a master journal file that should be written into the individual
** journal file. zMaster may be NULL, which is interpreted as no master
** journal (a single database transaction).
**
** This routine ensures that:
**
** * The database file change-counter is updated,
** * the journal is synced (unless the atomic-write optimization is used),
** * all dirty pages are written to the database file,
** * the database file is truncated (if required), and
** * the database file synced.
**
** The only thing that remains to commit the transaction is to finalize
** (delete, truncate or zero the first part of) the journal file (or
** delete the master journal file if specified).
**
** Note that if zMaster==NULL, this does not overwrite a previous value
** passed to an sqlite3PagerCommitPhaseOne() call.
**
** If the final parameter - noSync - is true, then the database file itself
** is not synced. The caller must call sqlite3PagerSync() directly to
** sync the database file before calling CommitPhaseTwo() to delete the
** journal file in this case.
*/
int sqlite3PagerCommitPhaseOne(
Pager *pPager, /* Pager object */
const char *zMaster, /* If not NULL, the master journal name */
int noSync /* True to omit the xSync on the db file */
){
int rc = SQLITE_OK; /* Return code */
if( pPager->errCode ){
return pPager->errCode;
}
PAGERTRACE(("DATABASE SYNC: File=%s zMaster=%s nSize=%d\n",
pPager->zFilename, zMaster, pPager->dbSize));
/* If this is an in-memory db, or no pages have been written to, or this
** function has already been called, it is a no-op.
*/
if( MEMDB && pPager->dbModified ){
sqlite3BackupRestart(pPager->pBackup);
}else if( pPager->state!=PAGER_SYNCED && pPager->dbModified ){
/* The following block updates the change-counter. Exactly how it
** does this depends on whether or not the atomic-update optimization
** was enabled at compile time, and if this transaction meets the
** runtime criteria to use the operation:
**
** * The file-system supports the atomic-write property for
** blocks of size page-size, and
** * This commit is not part of a multi-file transaction, and
** * Exactly one page has been modified and store in the journal file.
**
** If the optimization was not enabled at compile time, then the
** pager_incr_changecounter() function is called to update the change
** counter in 'indirect-mode'. If the optimization is compiled in but
** is not applicable to this transaction, call sqlite3JournalCreate()
** to make sure the journal file has actually been created, then call
** pager_incr_changecounter() to update the change-counter in indirect
** mode.
**
** Otherwise, if the optimization is both enabled and applicable,
** then call pager_incr_changecounter() to update the change-counter
** in 'direct' mode. In this case the journal file will never be
** created for this transaction.
*/
#ifdef SQLITE_ENABLE_ATOMIC_WRITE
PgHdr *pPg;
assert( isOpen(pPager->jfd) || pPager->journalMode==PAGER_JOURNALMODE_OFF );
if( !zMaster && isOpen(pPager->jfd)
&& pPager->journalOff==jrnlBufferSize(pPager)
&& pPager->dbSize>=pPager->dbFileSize
&& (0==(pPg = sqlite3PcacheDirtyList(pPager->pPCache)) || 0==pPg->pDirty)
){
/* Update the db file change counter via the direct-write method. The
** following call will modify the in-memory representation of page 1
** to include the updated change counter and then write page 1
** directly to the database file. Because of the atomic-write
** property of the host file-system, this is safe.
*/
rc = pager_incr_changecounter(pPager, 1);
}else{
rc = sqlite3JournalCreate(pPager->jfd);
if( rc==SQLITE_OK ){
rc = pager_incr_changecounter(pPager, 0);
}
}
#else
rc = pager_incr_changecounter(pPager, 0);
#endif
if( rc!=SQLITE_OK ) goto commit_phase_one_exit;
/* If this transaction has made the database smaller, then all pages
** being discarded by the truncation must be written to the journal
** file. This can only happen in auto-vacuum mode.
**
** Before reading the pages with page numbers larger than the
** current value of Pager.dbSize, set dbSize back to the value
** that it took at the start of the transaction. Otherwise, the
** calls to sqlite3PagerGet() return zeroed pages instead of
** reading data from the database file.
*/
#ifndef SQLITE_OMIT_AUTOVACUUM
if( pPager->dbSize<pPager->dbOrigSize
&& pPager->journalMode!=PAGER_JOURNALMODE_OFF
){
Pgno i; /* Iterator variable */
const Pgno iSkip = PAGER_MJ_PGNO(pPager); /* Pending lock page */
const Pgno dbSize = pPager->dbSize; /* Database image size */
pPager->dbSize = pPager->dbOrigSize;
for( i=dbSize+1; i<=pPager->dbOrigSize; i++ ){
if( !sqlite3BitvecTest(pPager->pInJournal, i) && i!=iSkip ){
PgHdr *pPage; /* Page to journal */
rc = sqlite3PagerGet(pPager, i, &pPage);
if( rc!=SQLITE_OK ) goto commit_phase_one_exit;
rc = sqlite3PagerWrite(pPage);
sqlite3PagerUnref(pPage);
if( rc!=SQLITE_OK ) goto commit_phase_one_exit;
}
}
pPager->dbSize = dbSize;
}
#endif
/* Write the master journal name into the journal file. If a master
** journal file name has already been written to the journal file,
** or if zMaster is NULL (no master journal), then this call is a no-op.
*/
rc = writeMasterJournal(pPager, zMaster);
if( rc!=SQLITE_OK ) goto commit_phase_one_exit;
/* Sync the journal file. If the atomic-update optimization is being
** used, this call will not create the journal file or perform any
** real IO.
*/
rc = syncJournal(pPager);
if( rc!=SQLITE_OK ) goto commit_phase_one_exit;
/* Write all dirty pages to the database file. */
rc = pager_write_pagelist(sqlite3PcacheDirtyList(pPager->pPCache));
if( rc!=SQLITE_OK ){
assert( rc!=SQLITE_IOERR_BLOCKED );
goto commit_phase_one_exit;
}
sqlite3PcacheCleanAll(pPager->pPCache);
/* If the file on disk is not the same size as the database image,
** then use pager_truncate to grow or shrink the file here.
*/
if( pPager->dbSize!=pPager->dbFileSize ){
Pgno nNew = pPager->dbSize - (pPager->dbSize==PAGER_MJ_PGNO(pPager));
assert( pPager->state>=PAGER_EXCLUSIVE );
rc = pager_truncate(pPager, nNew);
if( rc!=SQLITE_OK ) goto commit_phase_one_exit;
}
/* Finally, sync the database file. */
if( !pPager->noSync && !noSync ){
rc = sqlite3OsSync(pPager->fd, pPager->sync_flags);
}
IOTRACE(("DBSYNC %p\n", pPager))
pPager->state = PAGER_SYNCED;
}
commit_phase_one_exit:
if( rc==SQLITE_IOERR_BLOCKED ){
/* pager_incr_changecounter() may attempt to obtain an exclusive
** lock to spill the cache and return IOERR_BLOCKED. But since
** there is no chance the cache is inconsistent, it is
** better to return SQLITE_BUSY.
**/
rc = SQLITE_BUSY;
}
return rc;
}
/*
** When this function is called, the database file has been completely
** updated to reflect the changes made by the current transaction and
** synced to disk. The journal file still exists in the file-system
** though, and if a failure occurs at this point it will eventually
** be used as a hot-journal and the current transaction rolled back.
**
** This function finalizes the journal file, either by deleting,
** truncating or partially zeroing it, so that it cannot be used
** for hot-journal rollback. Once this is done the transaction is
** irrevocably committed.
**
** If an error occurs, an IO error code is returned and the pager
** moves into the error state. Otherwise, SQLITE_OK is returned.
*/
int sqlite3PagerCommitPhaseTwo(Pager *pPager){
int rc = SQLITE_OK; /* Return code */
/* Do not proceed if the pager is already in the error state. */
if( pPager->errCode ){
return pPager->errCode;
}
/* This function should not be called if the pager is not in at least
** PAGER_RESERVED state. And indeed SQLite never does this. But it is
** nice to have this defensive block here anyway.
*/
if( NEVER(pPager->state<PAGER_RESERVED) ){
return SQLITE_ERROR;
}
/* An optimization. If the database was not actually modified during
** this transaction, the pager is running in exclusive-mode and is
** using persistent journals, then this function is a no-op.
**
** The start of the journal file currently contains a single journal
** header with the nRec field set to 0. If such a journal is used as
** a hot-journal during hot-journal rollback, 0 changes will be made
** to the database file. So there is no need to zero the journal
** header. Since the pager is in exclusive mode, there is no need
** to drop any locks either.
*/
if( pPager->dbModified==0 && pPager->exclusiveMode
&& pPager->journalMode==PAGER_JOURNALMODE_PERSIST
){
assert( pPager->journalOff==JOURNAL_HDR_SZ(pPager) );
return SQLITE_OK;
}
PAGERTRACE(("COMMIT %d\n", PAGERID(pPager)));
assert( pPager->state==PAGER_SYNCED || MEMDB || !pPager->dbModified );
rc = pager_end_transaction(pPager, pPager->setMaster);
return pager_error(pPager, rc);
}
/*
** Rollback all changes. The database falls back to PAGER_SHARED mode.
**
** This function performs two tasks:
**
** 1) It rolls back the journal file, restoring all database file and
** in-memory cache pages to the state they were in when the transaction
** was opened, and
** 2) It finalizes the journal file, so that it is not used for hot
** rollback at any point in the future.
**
** subject to the following qualifications:
**
** * If the journal file is not yet open when this function is called,
** then only (2) is performed. In this case there is no journal file
** to roll back.
**
** * If in an error state other than SQLITE_FULL, then task (1) is
** performed. If successful, task (2). Regardless of the outcome
** of either, the error state error code is returned to the caller
** (i.e. either SQLITE_IOERR or SQLITE_CORRUPT).
**
** * If the pager is in PAGER_RESERVED state, then attempt (1). Whether
** or not (1) is succussful, also attempt (2). If successful, return
** SQLITE_OK. Otherwise, enter the error state and return the first
** error code encountered.
**
** In this case there is no chance that the database was written to.
** So is safe to finalize the journal file even if the playback
** (operation 1) failed. However the pager must enter the error state
** as the contents of the in-memory cache are now suspect.
**
** * Finally, if in PAGER_EXCLUSIVE state, then attempt (1). Only
** attempt (2) if (1) is successful. Return SQLITE_OK if successful,
** otherwise enter the error state and return the error code from the
** failing operation.
**
** In this case the database file may have been written to. So if the
** playback operation did not succeed it would not be safe to finalize
** the journal file. It needs to be left in the file-system so that
** some other process can use it to restore the database state (by
** hot-journal rollback).
*/
int sqlite3PagerRollback(Pager *pPager){
int rc = SQLITE_OK; /* Return code */
PAGERTRACE(("ROLLBACK %d\n", PAGERID(pPager)));
if( !pPager->dbModified || !isOpen(pPager->jfd) ){
rc = pager_end_transaction(pPager, pPager->setMaster);
}else if( pPager->errCode && pPager->errCode!=SQLITE_FULL ){
if( pPager->state>=PAGER_EXCLUSIVE ){
pager_playback(pPager, 0);
}
rc = pPager->errCode;
}else{
if( pPager->state==PAGER_RESERVED ){
int rc2;
rc = pager_playback(pPager, 0);
rc2 = pager_end_transaction(pPager, pPager->setMaster);
if( rc==SQLITE_OK ){
rc = rc2;
}
}else{
rc = pager_playback(pPager, 0);
}
if( !MEMDB ){
pPager->dbSizeValid = 0;
}
/* If an error occurs during a ROLLBACK, we can no longer trust the pager
** cache. So call pager_error() on the way out to make any error
** persistent.
*/
rc = pager_error(pPager, rc);
}
return rc;
}
/*
** Return TRUE if the database file is opened read-only. Return FALSE
** if the database is (in theory) writable.
*/
u8 sqlite3PagerIsreadonly(Pager *pPager){
return pPager->readOnly;
}
/*
** Return the number of references to the pager.
*/
int sqlite3PagerRefcount(Pager *pPager){
return sqlite3PcacheRefCount(pPager->pPCache);
}
/*
** Return the number of references to the specified page.
*/
int sqlite3PagerPageRefcount(DbPage *pPage){
return sqlite3PcachePageRefcount(pPage);
}
#ifdef SQLITE_TEST
/*
** This routine is used for testing and analysis only.
*/
int *sqlite3PagerStats(Pager *pPager){
static int a[11];
a[0] = sqlite3PcacheRefCount(pPager->pPCache);
a[1] = sqlite3PcachePagecount(pPager->pPCache);
a[2] = sqlite3PcacheGetCachesize(pPager->pPCache);
a[3] = pPager->dbSizeValid ? (int) pPager->dbSize : -1;
a[4] = pPager->state;
a[5] = pPager->errCode;
a[6] = pPager->nHit;
a[7] = pPager->nMiss;
a[8] = 0; /* Used to be pPager->nOvfl */
a[9] = pPager->nRead;
a[10] = pPager->nWrite;
return a;
}
#endif
/*
** Return true if this is an in-memory pager.
*/
int sqlite3PagerIsMemdb(Pager *pPager){
return MEMDB;
}
/*
** Check that there are at least nSavepoint savepoints open. If there are
** currently less than nSavepoints open, then open one or more savepoints
** to make up the difference. If the number of savepoints is already
** equal to nSavepoint, then this function is a no-op.
**
** If a memory allocation fails, SQLITE_NOMEM is returned. If an error
** occurs while opening the sub-journal file, then an IO error code is
** returned. Otherwise, SQLITE_OK.
*/
int sqlite3PagerOpenSavepoint(Pager *pPager, int nSavepoint){
int rc = SQLITE_OK; /* Return code */
int nCurrent = pPager->nSavepoint; /* Current number of savepoints */
if( nSavepoint>nCurrent && pPager->useJournal ){
int ii; /* Iterator variable */
PagerSavepoint *aNew; /* New Pager.aSavepoint array */
/* Either there is no active journal or the sub-journal is open or
** the journal is always stored in memory */
assert( pPager->nSavepoint==0 || isOpen(pPager->sjfd) ||
pPager->journalMode==PAGER_JOURNALMODE_MEMORY );
/* Grow the Pager.aSavepoint array using realloc(). Return SQLITE_NOMEM
** if the allocation fails. Otherwise, zero the new portion in case a
** malloc failure occurs while populating it in the for(...) loop below.
*/
aNew = (PagerSavepoint *)sqlite3Realloc(
pPager->aSavepoint, sizeof(PagerSavepoint)*nSavepoint
);
if( !aNew ){
return SQLITE_NOMEM;
}
memset(&aNew[nCurrent], 0, (nSavepoint-nCurrent) * sizeof(PagerSavepoint));
pPager->aSavepoint = aNew;
pPager->nSavepoint = nSavepoint;
/* Populate the PagerSavepoint structures just allocated. */
for(ii=nCurrent; ii<nSavepoint; ii++){
assert( pPager->dbSizeValid );
aNew[ii].nOrig = pPager->dbSize;
if( isOpen(pPager->jfd) && pPager->journalOff>0 ){
aNew[ii].iOffset = pPager->journalOff;
}else{
aNew[ii].iOffset = JOURNAL_HDR_SZ(pPager);
}
aNew[ii].iSubRec = pPager->nSubRec;
aNew[ii].pInSavepoint = sqlite3BitvecCreate(pPager->dbSize);
if( !aNew[ii].pInSavepoint ){
return SQLITE_NOMEM;
}
}
/* Open the sub-journal, if it is not already opened. */
rc = openSubJournal(pPager);
}
return rc;
}
/*
** This function is called to rollback or release (commit) a savepoint.
** The savepoint to release or rollback need not be the most recently
** created savepoint.
**
** Parameter op is always either SAVEPOINT_ROLLBACK or SAVEPOINT_RELEASE.
** If it is SAVEPOINT_RELEASE, then release and destroy the savepoint with
** index iSavepoint. If it is SAVEPOINT_ROLLBACK, then rollback all changes
** that have occurred since the specified savepoint was created.
**
** The savepoint to rollback or release is identified by parameter
** iSavepoint. A value of 0 means to operate on the outermost savepoint
** (the first created). A value of (Pager.nSavepoint-1) means operate
** on the most recently created savepoint. If iSavepoint is greater than
** (Pager.nSavepoint-1), then this function is a no-op.
**
** If a negative value is passed to this function, then the current
** transaction is rolled back. This is different to calling
** sqlite3PagerRollback() because this function does not terminate
** the transaction or unlock the database, it just restores the
** contents of the database to its original state.
**
** In any case, all savepoints with an index greater than iSavepoint
** are destroyed. If this is a release operation (op==SAVEPOINT_RELEASE),
** then savepoint iSavepoint is also destroyed.
**
** This function may return SQLITE_NOMEM if a memory allocation fails,
** or an IO error code if an IO error occurs while rolling back a
** savepoint. If no errors occur, SQLITE_OK is returned.
*/
int sqlite3PagerSavepoint(Pager *pPager, int op, int iSavepoint){
int rc = SQLITE_OK;
assert( op==SAVEPOINT_RELEASE || op==SAVEPOINT_ROLLBACK );
assert( iSavepoint>=0 || op==SAVEPOINT_ROLLBACK );
if( iSavepoint<pPager->nSavepoint ){
int ii; /* Iterator variable */
int nNew; /* Number of remaining savepoints after this op. */
/* Figure out how many savepoints will still be active after this
** operation. Store this value in nNew. Then free resources associated
** with any savepoints that are destroyed by this operation.
*/
nNew = iSavepoint + (op==SAVEPOINT_ROLLBACK);
for(ii=nNew; ii<pPager->nSavepoint; ii++){
sqlite3BitvecDestroy(pPager->aSavepoint[ii].pInSavepoint);
}
pPager->nSavepoint = nNew;
/* If this is a rollback operation, playback the specified savepoint.
** If this is a temp-file, it is possible that the journal file has
** not yet been opened. In this case there have been no changes to
** the database file, so the playback operation can be skipped.
*/
if( op==SAVEPOINT_ROLLBACK && isOpen(pPager->jfd) ){
PagerSavepoint *pSavepoint = (nNew==0)?0:&pPager->aSavepoint[nNew-1];
rc = pagerPlaybackSavepoint(pPager, pSavepoint);
assert(rc!=SQLITE_DONE);
}
/* If this is a release of the outermost savepoint, truncate
** the sub-journal to zero bytes in size. */
if( nNew==0 && op==SAVEPOINT_RELEASE && isOpen(pPager->sjfd) ){
assert( rc==SQLITE_OK );
rc = sqlite3OsTruncate(pPager->sjfd, 0);
pPager->nSubRec = 0;
}
}
return rc;
}
/*
** Return the full pathname of the database file.
*/
const char *sqlite3PagerFilename(Pager *pPager){
return pPager->zFilename;
}
/*
** Return the VFS structure for the pager.
*/
const sqlite3_vfs *sqlite3PagerVfs(Pager *pPager){
return pPager->pVfs;
}
/*
** Return the file handle for the database file associated
** with the pager. This might return NULL if the file has
** not yet been opened.
*/
sqlite3_file *sqlite3PagerFile(Pager *pPager){
return pPager->fd;
}
/*
** Return the full pathname of the journal file.
*/
const char *sqlite3PagerJournalname(Pager *pPager){
return pPager->zJournal;
}
/*
** Return true if fsync() calls are disabled for this pager. Return FALSE
** if fsync()s are executed normally.
*/
int sqlite3PagerNosync(Pager *pPager){
return pPager->noSync;
}
#ifdef SQLITE_HAS_CODEC
/*
** Set the codec for this pager
*/
void sqlite3PagerSetCodec(
Pager *pPager,
void *(*xCodec)(void*,void*,Pgno,int),
void *pCodecArg
){
pPager->xCodec = xCodec;
pPager->pCodecArg = pCodecArg;
}
#endif
#ifndef SQLITE_OMIT_AUTOVACUUM
/*
** Move the page pPg to location pgno in the file.
**
** There must be no references to the page previously located at
** pgno (which we call pPgOld) though that page is allowed to be
** in cache. If the page previously located at pgno is not already
** in the rollback journal, it is not put there by by this routine.
**
** References to the page pPg remain valid. Updating any
** meta-data associated with pPg (i.e. data stored in the nExtra bytes
** allocated along with the page) is the responsibility of the caller.
**
** A transaction must be active when this routine is called. It used to be
** required that a statement transaction was not active, but this restriction
** has been removed (CREATE INDEX needs to move a page when a statement
** transaction is active).
**
** If the fourth argument, isCommit, is non-zero, then this page is being
** moved as part of a database reorganization just before the transaction
** is being committed. In this case, it is guaranteed that the database page
** pPg refers to will not be written to again within this transaction.
**
** This function may return SQLITE_NOMEM or an IO error code if an error
** occurs. Otherwise, it returns SQLITE_OK.
*/
int sqlite3PagerMovepage(Pager *pPager, DbPage *pPg, Pgno pgno, int isCommit){
PgHdr *pPgOld; /* The page being overwritten. */
Pgno needSyncPgno = 0; /* Old value of pPg->pgno, if sync is required */
int rc; /* Return code */
Pgno origPgno; /* The original page number */
assert( pPg->nRef>0 );
/* If the page being moved is dirty and has not been saved by the latest
** savepoint, then save the current contents of the page into the
** sub-journal now. This is required to handle the following scenario:
**
** BEGIN;
** <journal page X, then modify it in memory>
** SAVEPOINT one;
** <Move page X to location Y>
** ROLLBACK TO one;
**
** If page X were not written to the sub-journal here, it would not
** be possible to restore its contents when the "ROLLBACK TO one"
** statement were is processed.
**
** subjournalPage() may need to allocate space to store pPg->pgno into
** one or more savepoint bitvecs. This is the reason this function
** may return SQLITE_NOMEM.
*/
if( pPg->flags&PGHDR_DIRTY
&& subjRequiresPage(pPg)
&& SQLITE_OK!=(rc = subjournalPage(pPg))
){
return rc;
}
PAGERTRACE(("MOVE %d page %d (needSync=%d) moves to %d\n",
PAGERID(pPager), pPg->pgno, (pPg->flags&PGHDR_NEED_SYNC)?1:0, pgno));
IOTRACE(("MOVE %p %d %d\n", pPager, pPg->pgno, pgno))
/* If the journal needs to be sync()ed before page pPg->pgno can
** be written to, store pPg->pgno in local variable needSyncPgno.
**
** If the isCommit flag is set, there is no need to remember that
** the journal needs to be sync()ed before database page pPg->pgno
** can be written to. The caller has already promised not to write to it.
*/
if( (pPg->flags&PGHDR_NEED_SYNC) && !isCommit ){
needSyncPgno = pPg->pgno;
assert( pageInJournal(pPg) || pPg->pgno>pPager->dbOrigSize );
assert( pPg->flags&PGHDR_DIRTY );
assert( pPager->needSync );
}
/* If the cache contains a page with page-number pgno, remove it
** from its hash chain. Also, if the PgHdr.needSync was set for
** page pgno before the 'move' operation, it needs to be retained
** for the page moved there.
*/
pPg->flags &= ~PGHDR_NEED_SYNC;
pPgOld = pager_lookup(pPager, pgno);
assert( !pPgOld || pPgOld->nRef==1 );
if( pPgOld ){
pPg->flags |= (pPgOld->flags&PGHDR_NEED_SYNC);
sqlite3PcacheDrop(pPgOld);
}
origPgno = pPg->pgno;
sqlite3PcacheMove(pPg, pgno);
sqlite3PcacheMakeDirty(pPg);
pPager->dbModified = 1;
if( needSyncPgno ){
/* If needSyncPgno is non-zero, then the journal file needs to be
** sync()ed before any data is written to database file page needSyncPgno.
** Currently, no such page exists in the page-cache and the
** "is journaled" bitvec flag has been set. This needs to be remedied by
** loading the page into the pager-cache and setting the PgHdr.needSync
** flag.
**
** If the attempt to load the page into the page-cache fails, (due
** to a malloc() or IO failure), clear the bit in the pInJournal[]
** array. Otherwise, if the page is loaded and written again in
** this transaction, it may be written to the database file before
** it is synced into the journal file. This way, it may end up in
** the journal file twice, but that is not a problem.
**
** The sqlite3PagerGet() call may cause the journal to sync. So make
** sure the Pager.needSync flag is set too.
*/
PgHdr *pPgHdr;
assert( pPager->needSync );
rc = sqlite3PagerGet(pPager, needSyncPgno, &pPgHdr);
if( rc!=SQLITE_OK ){
if( pPager->pInJournal && needSyncPgno<=pPager->dbOrigSize ){
sqlite3BitvecClear(pPager->pInJournal, needSyncPgno);
}
return rc;
}
pPager->needSync = 1;
assert( pPager->noSync==0 && !MEMDB );
pPgHdr->flags |= PGHDR_NEED_SYNC;
sqlite3PcacheMakeDirty(pPgHdr);
sqlite3PagerUnref(pPgHdr);
}
/*
** For an in-memory database, make sure the original page continues
** to exist, in case the transaction needs to roll back. We allocate
** the page now, instead of at rollback, because we can better deal
** with an out-of-memory error now. Ticket #3761.
*/
if( MEMDB ){
DbPage *pNew;
rc = sqlite3PagerAcquire(pPager, origPgno, &pNew, 1);
if( rc!=SQLITE_OK ) return rc;
sqlite3PagerUnref(pNew);
}
return SQLITE_OK;
}
#endif
/*
** Return a pointer to the data for the specified page.
*/
void *sqlite3PagerGetData(DbPage *pPg){
assert( pPg->nRef>0 || pPg->pPager->memDb );
return pPg->pData;
}
/*
** Return a pointer to the Pager.nExtra bytes of "extra" space
** allocated along with the specified page.
*/
void *sqlite3PagerGetExtra(DbPage *pPg){
Pager *pPager = pPg->pPager;
return (pPager?pPg->pExtra:0);
}
/*
** Get/set the locking-mode for this pager. Parameter eMode must be one
** of PAGER_LOCKINGMODE_QUERY, PAGER_LOCKINGMODE_NORMAL or
** PAGER_LOCKINGMODE_EXCLUSIVE. If the parameter is not _QUERY, then
** the locking-mode is set to the value specified.
**
** The returned value is either PAGER_LOCKINGMODE_NORMAL or
** PAGER_LOCKINGMODE_EXCLUSIVE, indicating the current (possibly updated)
** locking-mode.
*/
int sqlite3PagerLockingMode(Pager *pPager, int eMode){
assert( eMode==PAGER_LOCKINGMODE_QUERY
|| eMode==PAGER_LOCKINGMODE_NORMAL
|| eMode==PAGER_LOCKINGMODE_EXCLUSIVE );
assert( PAGER_LOCKINGMODE_QUERY<0 );
assert( PAGER_LOCKINGMODE_NORMAL>=0 && PAGER_LOCKINGMODE_EXCLUSIVE>=0 );
if( eMode>=0 && !pPager->tempFile ){
pPager->exclusiveMode = (u8)eMode;
}
return (int)pPager->exclusiveMode;
}
/*
** Get/set the journal-mode for this pager. Parameter eMode must be one of:
**
** PAGER_JOURNALMODE_QUERY
** PAGER_JOURNALMODE_DELETE
** PAGER_JOURNALMODE_TRUNCATE
** PAGER_JOURNALMODE_PERSIST
** PAGER_JOURNALMODE_OFF
** PAGER_JOURNALMODE_MEMORY
**
** If the parameter is not _QUERY, then the journal_mode is set to the
** value specified if the change is allowed. The change is disallowed
** for the following reasons:
**
** * An in-memory database can only have its journal_mode set to _OFF
** or _MEMORY.
**
** * The journal mode may not be changed while a transaction is active.
**
** The returned indicate the current (possibly updated) journal-mode.
*/
int sqlite3PagerJournalMode(Pager *pPager, int eMode){
assert( eMode==PAGER_JOURNALMODE_QUERY
|| eMode==PAGER_JOURNALMODE_DELETE
|| eMode==PAGER_JOURNALMODE_TRUNCATE
|| eMode==PAGER_JOURNALMODE_PERSIST
|| eMode==PAGER_JOURNALMODE_OFF
|| eMode==PAGER_JOURNALMODE_MEMORY );
assert( PAGER_JOURNALMODE_QUERY<0 );
if( eMode>=0
&& (!MEMDB || eMode==PAGER_JOURNALMODE_MEMORY
|| eMode==PAGER_JOURNALMODE_OFF)
&& !pPager->dbModified
&& (!isOpen(pPager->jfd) || 0==pPager->journalOff)
){
if( isOpen(pPager->jfd) ){
sqlite3OsClose(pPager->jfd);
}
pPager->journalMode = (u8)eMode;
}
return (int)pPager->journalMode;
}
/*
** Get/set the size-limit used for persistent journal files.
**
** Setting the size limit to -1 means no limit is enforced.
** An attempt to set a limit smaller than -1 is a no-op.
*/
i64 sqlite3PagerJournalSizeLimit(Pager *pPager, i64 iLimit){
if( iLimit>=-1 ){
pPager->journalSizeLimit = iLimit;
}
return pPager->journalSizeLimit;
}
/*
** Return a pointer to the pPager->pBackup variable. The backup module
** in backup.c maintains the content of this variable. This module
** uses it opaquely as an argument to sqlite3BackupRestart() and
** sqlite3BackupUpdate() only.
*/
sqlite3_backup **sqlite3PagerBackupPtr(Pager *pPager){
return &pPager->pBackup;
}
#endif /* SQLITE_OMIT_DISKIO */

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